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Notes on 
Heating and 
Ventilation 



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COPYRIGHT DEPOSrr. 



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NOTES 



ON 



HEATING AND VENTILATION 



BY 



JOHN R. ALLEN 

fi 

JUNIOR PROFESSOR MECHANICAL ENGINEERING 
UNIVERSITY OF MICHIGAN 

Member American Society Heating and Ventilating 

Engineers 

Member American Society Mechanical 
Engineers 



SECOND EDITION 



» 5 

13 3 




DOMESTIC ENGINEERING 


CHICAGO 




49-53 North Jefferson 


Street 


1906 





|UBRARY ot CONGrtESS, 
two Copies Heceivdd 

JUL 3 1^08 
(Uu,f7 f906 

COPY tiJ 




K 



COPYRIGHT 

DOMESTIC ENGINEERING 

1906 



V 






^ 



PREFACE. 

The chapters comprising this book are a brief resume 
of the lectures delivered by the author to the classes in 
heating and ventilation at the University of Michigan. 
The subject matter was first published as a series of 
articles in Domestic Exgixeeeing. 

The book has been written primarily for the steam- 
fitter and designer of heating systems. It presupposes 
a knowledge of the construction and operation of the 
simpler forms of heating* systems and has been reduced 
to as brief a form as possible so that the reader can 
readily find the notes or data desired. 

The design of heating and ventilating systems has 
not been reduced to an exact science. The factor of 
judgment and experience in designing heating plants is 
a large one. One reason for this is the lack of exact 
experimental data governing some of the most important 
factors entering into these calculations. This lack must 
be filled from the designer's experience. 

The tables of heat losses from radiating surfaces and 
the tests of pipe coverings have been compiled from the 
results obtained from the experiments made under the 
direction of Prof. M. E. Cooley, Dean of the Department 
of Engineering, University of Michigan. The author also 
has shown illustrations of tunnel sections which have 
been used by Prof. Cooley in the design of a number of 
central heating systems. John R. AI/LEN. 

Ann Arbor, October 80, 1905. 



TABLE OF CONTENTS. 



Introduction. 

Theory of heat and measurement of tempera- 
ture . . . . . . . .II 

Chapter I. 

Heat losses from buildings and rules for deter- 
mining the heat losses in different construc- 
tions ........ 17 

Chapter II. 

Dift'erent forms of heating systems ; their ad- 
vantages, disadvantage and relative economy 36 

Chapter III. 

The design of a direct steam heating system 
and the properties of steam . . . -49 

Chapter IV. 
Design of an indirect steam heating system . 81 

Chapter \'. 

Steam boilers and steam piping. Determination 
of size and details of construction . . . 95 



Chapter VI. 

The connection of mains to risers and risers to 
radiators, with ilkistrations of different ar- 
rangements in practical use . . . .122 

Chapter VII. 
The design of a hot water heating system . 147 

Chapter MIL 
Hot water boilers and piping. Determination 



of size and details of construction 



DO 



Chapter IX. 

\>ntilation and the pollution of air by human 
beings, artificial lighting and chemical pro- 
cesses . . . . . . . .172 

Chapter X. 
Design of hot air heating system . . .186 

Chapter XI. 

Fan systems of heating, with tables of fan 
capacities and condensation in heater coil . 200 

Chapter XII. 

Central heating systems ; their design and in- 
stallation, with discussion of different meth- 
ods of carrying pipes underground . . 226 

Chapter XIII. 

Pipe cov(Tings, pipe, valves, temperature regu- 
lation, air washing and exhaust heating . 252 



SUBJECT INDEX. 



Page. 



A 



Absolute temperature .... 12 
Air. changes of. for venti- 
lation 177 

dilution of. for chem- 
icals 175 

flues 88-91-181-191-192 

loss of pressure in pipes. 218 

mixing systems 220 

moistening of . . 188-264-265 

piping systems 263 

pollution of 173 

registers, location of... 181 

valves 170-244-256 

velocity of. in pipes .... 

192-211-214-216 

washers 265 

Anchors for steam pipes.. 243 



B 



Blowers, steel plate 
Boilers — 

cast iron, proportions of. 



205-106 



central heating 



100 

227 
99 

158 
98 
95 
52 



•:>7 



horsepower of 

hot water 

proportions of 

types of , 

Boiling point of water. . . . 
Brick walls, heat loss 

through 

Buildings, example of heat 

loss from 33 

heat loss from 17-27-28 

materials, heat loss from 12 

C 

Carbon dioxide, amount al- 
lowable 177 

Cast iron boilers, propor- 
tions of 100 

radiators, heat loss from 55 
Ceilings, heat loss from. . . 27 
Central heating, air valves 

for 244 

boilers for 227 

carrying of pipes for... 235 
design and location. .. .226 
gravity system 229 



Page. 
Central beating, heat and 

power combined 222 

high pressure system... 1 30 

low pressure 231 

pump logs 236 

size of pipes 240 

systems of distribution . 228 

tunnels 237 

Coils, heating for fan sys- 
tem \ .269 

pipe, heat loss f rom .. 55-64 

Cold air duct 189 

Conduction 22 

Connections, mains to 

risers 122 

radiator, single pipe. . . .134 

radiator, two-pipe 141 

Convection, loss by 23 

Covering for steam pipe .. 252 

relative value of 253 

varying thickness 254 

varying pressure 255 



D 



Dampers for hot air flues.. 191 

Damper regulators 264 

Dams in return pipes 102 

Direct steam heating 

41-49 55-75 

radiation, example of . . . 77 

Disc fans 2i 2-223 

Doors, heat loss from. ... 27 
Draining of steam pipes.. 102 

Drips 101 

Ducts, cold air 189 

for fan system 214 

for recirculating 190 

underground piping .... 235 

E 

Economizers 250 

Economy of different heat- 
ing systems 36-46 

Example. direct steam 

heating 75 

fan heatino- 223 

heat loss from buildings 33 



rage. 
Example, heat lost bv con- 
duction 23 

heat lost by radiation. .. 21 

hot air heating 196 

hot water heating 152 

indirect heating 90 

specific heat 14 

size of steam main 11.3 

in use of steam tables. . 53 
Exhaust steam heating. . .232 
steam and hot water 

heating 249 

Expansion "of steam pipes. 

101-llS 

tanks 157 

Evaporation, latent heat of 52 
total heat of 52 

F 

Factors for exposure 27 

Fan coils 209-212 

heaters, dimensions of..il3 
loss of heat from. . .210-215 
heating, air to be sup- 
plied 203 

systems of heating. . 44-200 

Fans, disc 222-223 

steel plate 205-206 

Fahrenheit temperature... 12 

Fittings 260 

Flow main 157 

riser 157 

of hot water in pipes. . .168 
Floors, heat lost from.... 27 

Flues, foul air 193 

friction in . . ,- 218 

hot air 91-191 

materials for 220 

proportions of 192 

recirculating 190 

for indirect radiators. . . 91 

Flue radiators 65-92-94 

Furnaces, for hot air 

39-187-195 

Fuel 99 

G 
Gases, specific heat of.... 15 

Grates, heating by 37 

Grates, proportions of . .98-195 
Gravity system 110-229 

II 

Hangers for pipes 243 

Heat 11 

conduction of 22 

convection of 23 

latent 51-52 

given off by human be- 
ings 175 

given off by illuminants. 177 



rage. 
Heat loss from buildinus.. 

17-25-27-28-31 

loss from direct radia- 
tors 55 

loss, effect of height on. 25 
loss from fan heater 

coils 210 

loss from flue radiators. 65 
loss from hot water ra- 
diators 149 

loss from indirect ra- 
diators 65 

loss from pipe cover- 
ings 253 

radiation of 18 

specific 14 

transmission of, in build- 
ings 27 

unit of 13 

relation to work 13 

Heater coils for fan svs- 

tem 209-212 

Heating apparatus, classi- 
fication of 36 

by direct steam 49 

by exhaust steam 232 

bv fan svstem 200 

by hot air 186 

by hot water 147 

by high pressure steam. 230 

by indirect steam 81 

by low pressure steam.. 232 

surface 98 

Horespower of steam boil- 
ers 100 

for disc fan 222 

for steel plate fan.. 205-206 
Hot air, heating, example 

of : 196 

furnace 39-187-194 

flues 91-191-192 

Hot water heating, bo'l- 

ers 155-158 

pump system 249 

mains, size of 169 

natural system 147 

open and closed circuits. 166 

piping 157-160-169 

piping, velocitv of flow 

in 168 

radiators 148 

risers, size of 171 

rules for 152 

sing-le pipe svstem 166 

Ilumiditv . . . ." 188-264 



Indirect heating, example 

of 90 

rules for 89 



Page. 
Indirect heating, hot water. 43 

radiators S'2-So-SS 

steam 43-81 

L 

Latent heat 51-52 

Lighting, pollution of air 

by 174 

heat given off bj' 177 

Magnesia pipe covering. 

loss from 253 

Mains, return . lUl-115-116-122 
steam ..101-112-114-116-122 

Moistening of air lSS-265 

Mineral wool covering. .. .253 

O 

Overhead steam mains. . . .110 
hot water mains 162 

P 

Pipe covering 252 

Pipes, expansion of 118 

Piping 101-155-260 

hangers and anchors for. . 243 

capacitv of 114-169 

for steam . .101-104-112-122 
for hot water. .157-160-169 

pitch of • 102-158-160 

underground systems. . .153 

Properties of steam 49 

Pump logs 237 

R 

Radiation 18 

Radiators, connection of.. 134 

flue 65-94 

heat loss from 68 

hot water 148-152-169 

• indirect steam .. 82-85-89-90 
installation of indirect. 85 
steam . . . .54-56-68-69-71-75 

tappings 85 

Registers SS-181-191 

Regulation of tempera- 
ture 261 

Reliefs 101 

Resistance of air flues.... 218 
Return mains. 101-112-116-157 

Risers 101-122-157 

Rules for. direct steam 

heating 72-73 

fan heating coil 211 

heat lost from build- 
ings 29-31 

horsepower of fan 207 



Page. 
Rules for, hot water heat- 
ing 151 

hot water piping 170 

hot air heating 195 

hot air piping 194 

indirect steam heating. . 89 
steam pipe sizes 114 

S 

Siphon 102 

Skylights, heat loss from. 27 

Specific heat 14 

Steam boilers 95-98 

cast iron 100 

heating, direct 

41-47-104-114 

bv exhaust 232 

indirect 43-81 

mains 

. .102-112-114-116-121-122 

piping 101-104-122 

pipes, expansion of 118 

radiators, direct 54-56 

flue 65 

indirect 82 

resistance in pipes 242 

tables 51 

traps 104 

Steel plate blowers 204 

Stoves, heating by 38 

T 
Tables, air dilution for 

chemicals 176 

changes of air for venti- 
lation 179 

conducting power 22 

example for direct ra- 
diation 77 

example for hot water 
heating 153 

example of hot air sys- 
tem 197 

example of indirect heat- 
ing 92 

fan heater dimensions .. 213 

heat loss from direct ra- 
diation 55-68 

heat loss from flue ra- 
diators 65 

heat loss from indirect 
radiators 67-84 

heat loss from hot water 
radiators 149 

heat loss from fan coils . 
210-215-216 

heat loss from pipe cov- 
erings 253-254-255 

heat given off by illumi- 
nants 177 



Page. 
Tabk'S, hot air systems, 

proportions of 194 

porportions of cast iron 

boilers lOU-158 

products of respiration 

from human beings.. 174 
products of combustion 

from sources of light. 174 
properties of steam .... 52 

radiating power 19 

resistance of air flows. .218 
size of flues for indirect 

radiation 88 

size of hot water mains. 

109-171 

size of steam and return 

mains 114-1 IG 

specific heat 14 

speed and capacity of 

disc fans 222 

speed and capacity of 

steel plate fans. ".205-206 
temperature of air leay- 

ing indirect radiators 85 



Page. 
Tables, velocity of flow in 

hot water system .... 1G8 

Thermal units 11 

Temperature absolute .... 12 
of air leaving hot air 

furnace 195 

Fahrenheit 12 

regulation 261 

Tunnels 287 

V 

Vacuum heating systems.. 268 

Valves Il21-233-26() 

air 244-256 

Ventilation 172-180 

W 

Water hammer 103 

line in heating system.. 102 
seal ^ 102 

Windows, heat lost from. . 27 

Wooden houses, heat lost 

from 27 

Work, relation to heat.... 13 



NOTES ON 


H EATING 


AND 


VENTILATION 





INTROD UCTION. 

HEAT. 

Heat is a form of motion. The modern scientific 
conception of heat is that it is produced by the mo- 
tion of the particles of matter 
which compose any body. Ah Heat. 

matter is conceived as being 
made up of small particles called molecules. These 
particles do not exist in a state of rest, but are in 
constant vibration. If these particles move slowly 
the body is at a low temperature ; if they move 
more rapidly the body is at a higher temperature, 
the temperature of the body being determined by 
the rapidity of the motion of the particles. In 
measuring heat there are two properties to be con- 
sidered — the intensity and the quantity. This may 
be compared to measuring water in a pipe. We 
measure the pressure of the water in the pipe by 
means of a gauge in pounds per square inch. The 
quantity of water is measured in pounds. In the 
same way the intensity of heat is measured by the 
thermometer in degrees and the quantity of heat is 



12 Notes on Heating and Ventilation 

measured by comparison with the quantity of heat 
which a pound of water will absorb. 

Temperature, which is a measure of the intensity 
of the heat of a body, might also be considered as 

measuring the velocity of the 
Temperature. molecules of the body. In me- 

chanical engineering all meas- 
urements of temperature are made on the Fahren- 
heit scale. On this scale the freezing point is taken 
at 32° and the boiling point as 212°, the tube of the 
thermometer between these points being divided 
into 180 equal parts called degrees. 

We never know the total amount of heat in a 
body. As it is impossible to bring any body to a 
condition of absolutely no heat, the heat in any body 
must always be measured from some assumed zero 
point and in the Fahrenheit scale this assumed zero 
point is 2^2"" below the freezing point. For theoreti- 
cal purposes, however, it is highly desirable to have 
some absolute standard of heat. A perfect gas at 
7^2"" contracts about 1/493 of its volume for each 
degree Fahrenheit that it is reduced in temperature. 
If, then, we keep on decreasing the temperature of 
a perfect gas from 7,2°, until it reaches a point 493° 
below 32° Fahrenheit, it would have, theoretic- 
ally, no volume. If it has no volume, the amount 
of heat which it contains must be zero. This point, 
then, is called the absolute zero. This point is mani- 
festly an ideal one. To find the absolute tempera- 



Notes on Heating and Ventilation 13 

ture in degrees it is necessary to add to the Fahren- 
heit temperature 461 degrees, that is, 1,2° Fahren- 
heit corresponds to 493° absolute. 

Heat is not a substance and it can not be meas- 
ured as we would measure water in pounds or cubic 
feet, but it must be measured by 
the effect which it produces. Unit of Heat. 
Suppose it requires a certain 
amount of heat to raise a pound of water from 39° 
to 40° Fahrenheit. It would require three times 
that quantity of heat to raise a pound of water from 
39° to 42° Fahrenheit. The heat required to raise 
a pound of water one degree Fahrenheit is called a 
British thermal unit, and is designated by letters 
B. T. U. 

Work is measured in foot-pounds. The unit of 

work is the work required to raise one pound 

through a height of one foot. 
^ .^ <. . . r ^ Relation Between 

ten units of work or ten foot- „ ^ ^ ,Tr , 

Heat and Work. 

pounds would be the amount of 
work done in raising ten pounds one foot high or 
one pound ten feet high. Heat is a form of 
motion, hence there must be some definite relation 
between heat and work. This relation was first 
determined by Joule. By a series of experiments 
Joule found that one heat unit was equivalent to 
778 foot-pounds. It is possible, then, to express 
heat either in heat units or in foot-pounds. 



1^ Notes on Heating and Ventilation 

Different substances require very different quanti- 
ties of heat to produce the same change of tempera- 
ture for the same weight. As 
Specific Heat. for example, to raise one pound 

of water one degree requires one 
B. T. U. ; to raise one pound of ice one degree re- 
quires .504 B. T. U/s ; to raise one pound of 
wTOught iron one degree requires .1138 B. T. U. 
The heat necessary to raise one pound of a sub- 
stance one degree, expressed in British thermal 
units, is called specific heat. The following table 
gives the specific heat of the principal substances 
which we meet with in engineering work :, 



Table 1. — Specific Heat. 



Substance — B. T. U. 

Water 1 

ce 504 

Glass 197 

Cast iron 1298 

Soft steel 1165 

Wrought iron 1138 

Copper 0951 

Brass 0939 

Tin 0569 

Lead 0314 



It is required to raise the temperature of a cast 
iron radiator weighing 300 pounds from 70° to 

212°. The temperature through 
Example. which the iron would be raised 

would then be 212 minus 70° or 
142°. From the table we see that it would require 
to raise one pound of cast iron one degree .1298 heat 



Notes on Heating\and Ventilation 1'^ 

» 

units, then to raise one pound 142° would require 
142 times .1298 or 18.43 heat units, and to raise 
300 pounds one degree would require 300 times this 
amount or 5,529 B. T. U/s, the heat required to 
heat the radiator. 

In solid substances the change in volume when 
they are heated is so small that it is not considered. 
In gases, however, the change in volume when the 
gas is heated without being confined, depends di- 
rectly upon the absolute temperature and may be 
very large. When air is confined and is heated, it 
cannot expand; if it does not expand there is no 
work done because, from our definition of work, it 
is necessary when work is done, that the body have 
some movement. On the other hand, when air re- 
ceives heat and is free to expand it does work. For 
instance, if air were confined in a cylinder by a pis- 
ton, and this air were heated, the air would expand 
and the piston would be moved out. As the piston 
is moved through a certain space there must be 
work done. On the other hand, if the piston were 
blocked so that it could not move, then the air on 
being heated would do no work. Then in these two 
cases dififerent amounts of heat will be required to 
raise the substance one degree, depending upon 
whether there is external work done or not. 

It is necessary in gases that we consider two 
specific heats, the specific heat of constant volume 
and the specific heat of constant pressure. For air 



16 Notes on Heating and Ventilation 

the specific heat of constant volume is .1689, ^^^ 
constant pressure it is .2375. It is seldom that we 
use air in a confined space, so that, so far as this 
work is concerned, we shall in most cases consider 

the specific heat of air as .2375 — that is, to raise one 
pound of air one degree requires .2375 B. T. U., 
the pressure being constant. 



CHAPTER L 



HEAT LOSS FROM BUILDINGS. 

Heat is lost from a room in three ways — by the 

direct transmission of the heat through the walls 

and windows ; by the passage of 

,. r , ' n 1 1 Loss of Heat. 

air up the foul air flues, and by ^^^^ Buildings. 

the filtration of air through the 

walls and air leakage around doors and windows. 

The first two losses are easily determined, but the 

determination of the loss by filtration must always 

involve a large factor of judgment and experience. 

All building construction is more or less porous. 

This is well exemplified by the old experiment made 

with a common brick. . Two cornucopias of paper 

are pasted on opposite sides of a common brick, the 

large end of the cornucopias being fastened to the 

brick. Opposite the small end of the cornucopia at 

one side is placed a lighted candle. By blowing into 

the cornucopia on the opposite side, the candle may 

be blown out, the air having passed directly through 

the brick. 

* 
The experiments which have been made in order 

to determine this loss generally tend to show that 

in the ordinary well-constructed building the air in 

the room will change about once per hour, when all 

doors and windows are closed. 



18 XcjTEs UN Heating and Ventilation 

In order to study the other heat losses from a 
room it will be necessary to study the laws of cool- 
ing. A body may be cooled in three different w^ays 
— by radiation, by conduction and by convection 
(contact of air). In order to understand these losses 
more thoroughly, each will be considered separately. 

The heat that passes from a body by radiation 
may be considered similar to the light which is given 

off by a lamp. There is always 
Badiation. a transfer of radiant heat from 

the body of a higher tempera- 
ture to the body of lower temperature. The amount 
of heat radiated will depend upon the difference in 
temperature betv/een the bodies and the substance 
through which this heat passes and the condition of 
the surface from wdiich the heat is radiated. 

The losses bv radiation mav be better understood 
by referring to Fig. i. Suppose the plate PP to be 
of cast iron i foot square and i inch thick. Let us 
suppose this place to be on both sides at a tempera- 
ture of 60°. Let this plate form one side of a room, 
the w^alls WWW being non-conducting substances 
and at a temperature of 59°, the air in this space 
being at a temperature of 60°. Since the plate and 
the air in the space are at the same temperature, 
there will be no loss of heat from the air to the 
walls, but all the heat that passes from the plate PP 
to the walls must pass by radiation. For ordinary 
temperatures of heating surfaces, say 60 or 70°, the 



Notes on Heating and Ventilation 19 

loss by radiation will equal the difference in tem- 
perature between the hot body and the cold body 
multiplied by a factor representing the radiating 
power of the body. The following table gives the 
radiating power of dift'erent substances : 



Table II — Radiating Power. 



Radiating power of bodies, expressed in heat units, 
given off per square foot pei* hour for a difference of 
one degree Fahrenheit. (Peclet.) 

Copper, polished 0327 

Iron, sheet 0920 

Glass 595 

Cast iron, rusted 648 

Building stone, plaster, wood, brick 7358 

Woolen stuffs, anv color 7522 

Water 1.085 



Heat is radiated in straight lines exactly as light 
is given oft from the source of light. We may have 
heat shadows the same as we have light shadows 
and the intensity of the heat is inversely propor- 
tional to the square of the distance from the source. 
Some bodies are transparent to heat and other 
bodies absorb heat, the same as some bodies are 
transparent to light and others absorb light. The 
transparency of bodies to heat is called diather- 
mancy. Gases, such as air, oxygen, nitrogen, and 
hydrogen, are almost perfectly transparent to heat, 
Vvdiile wood, hair, felt and other non-conducting 
bodies are almost perfectly opaque to the transmis- 
sion of heat. The loss of heat by radiation is inde- 
pendent of the form of a body so long as it does not 



20 



Notes on Heating and Ventilation 



radiate heat to itself. The color or condition of the 
surface of different bodies affects their radiant 
power. Smoothly polished surfaces radiate less 
heat than rough surfaces. As, for instance, a sur- 




Figure 1. 



face painted with lamp black will radiate over 13 
times as much heat as a polished copper surface. 

Suppose we have a glass surface five square feet 
in area. The glass surface is at a temperature of 



Notes ox Heating axd Ventilation 



21 



70° and the objects surrounding 
it are at a temperature of zero. Example. 

From the table we see that one 
square foot of glass (surface) loses .595 heat units 
in an hour for a difference of one degree between 




Figure 2. 



it and the surrounding objects. For a .difference of 
70°, then, each square foot of glass would lose 70 
times that amount, or 41.5 heat units, and 5 square 



22 Notes on Heating and Ventilation 

feet of glass would lose 5 times that amount, or 
207.5 heat and units per hour. 

The heat transmitted by conduction is the heat 
which is transmitted through the body itself. For 

example, take the condition 
Conduction. shown in Fig. 2. PP is a plate, 

one side of which is enclosed by 
the walls WW. Let the temperature of the plate 
outside be 59°, the temperature on the inside of the 
plate be 60° ; the temperature of the walls be 60°, 



Table III — Conducting Power. 



The conducting power of materials, expressed in the 
quantity of heat units transmitted per square foot per 
hour b}^ a plate one inch thick, the surfaces on the two 
sides .of the plate differing in temperature by one de- 
gree. (Pec let.) 

B. T. U's. 

Copper 515 

Iron 233 

Lead 113 

Stone 16.7 

Glass 6.6 

Brick work 4.8 

Plaster 3.8 

Pine wood .75 

Sheep's wool .323 



the temperature of the air in the room be 6o°. Then 
all the heat that is lost by the room must be lost by 
direct conduction through the plate PP. The 
amount of heat conducted will depend upon the ma- 
terial of which the conductor is composed and in ad- 
dition it will also depend upon the difference in 
temperature between the two sides of the plate and 
upon the thickness of the plate. The conduction 
through any plate may be calculated as follows : 



Notes ox Heating and Ventilation 28 

Multiply the factor given in Table III by the differ- 
ence in temperature between the two sides of the 
plate and divide the result by the thickness of the 
plate in inches. The quotient will be the heat trans- 
mitted l:y conduction per square foot of surface. 

Suppose a boiler plate 5 feet square, 32"ii^cl^ thick, 
to have a temperature of 70" on one side and a tem- 
perature on the opposite of 200^. 
The dift'erence in temperature of Example, 

the two sides of the plate would 
be 130°. The amount of heat conducted would then 
be 233x130^-1 '2=15145 B. T. U.'s, the heat trans- 
mitted per square foot of plate. Then five square 
feet would transmit five times this amount, or 75,725 
B. T. U.'s in one hour. 

Loss by convection is sometimes termed loss by 
contact of air. Take, for example, the condition 
shown in Fig. 3. Let P be a 
vertical plane of metal one foot Convection, 

square, having its surfaces main- 
tained at 60° temperature. Let the walls WW also 
be at a temperature of 60°. Let the air in the room 
be 59°. Li this case there will be no loss of heat 
from the walls to the plate by radiation and there 
will be no loss through the plate by conduction, but 
heat will be transmitted from che walls and the plate 
to the air of the room. The air which comes in con- 
tact with the warmer walls will be heated. As air 
is heated it becomes liehter and rises and a current 



24 



Notes on Heating and Ventilation 



is formed. This produces a circulation of air, and 
this circulation of air gives rise to a loss of heat by 
convection or contact of air. 

The loss of heat by convection is independent of 
the nature of the surface, wood, stone or iron losing 




Figure 3. 



tiiC same quantity of heat, but it is affected by the 
form of the body — that is, a cyHnder and a sphere 
would lose different amounts of heat per square 
foot. Take the steam radiator, for example. The 



Notes on Heating and Ventilation '^^ 

air nearest the radiator becomes heated and rises ; 
as it rises its place is taken by other colder air com- 
ing off the floor so that a current of air is estab- 
lished. In the ordinary type of radiator, the loss 
by contact of air represents about half the loss of 
heat, the .balance being loss by radiation. 

The calculation of the heat lost by convection is 
quite complicated and dift'erent expressions have 
been derived for this loss for dif- 
ferent forms of surfaces. Those Calculation of 
developed by Peclet are given in Convection 

Box's treatise on Heat. " Losses. 

The rules given for convection 
in the text-books on heat cannot, as a rule, be ap- 
plied to the loss of heat from buildings. All these 
rules assume that the air surrounding the object is 
in a perfectly quiescent state. In buildings this is 
not the case, for the air surrounding a building is 
rapidly circulated by the winds. Theoretically a high 
building would lose proportionally less heat than a 
low building, because in the upper stories there 
would be a smaller difference in temperature be- 
tween the air inside the room and the air outside 
than in the lower stories. This, however, is not the 
case, as the wind circulates the air outside the build- 
ing and makes the temperature of the air surround- 
ing the building on the outside practically the same 
at all levels. 

Inside the room, however, the air at the top of the 



'^6 XoTEi Ox\ Heating and Ventilation 

rocm is much warmer than that at the floor. The 
result is that the rate of transmission of heat in 
rooms with high ceihngs is appreciably higher than 
in rooms with low ceilings, as in the room with a 
high ceiling we have a greater difiference of tem- 
perature between the inside and the outside air at 
the ceiling. This difiference is not ordinarily consid- 
ered unless the height of the room exceeds ten feet. 
If the hei2:ht of the room does not exceed ten feet 
the temperature taken live feet above the floor line 
may be assumed at the average temperature in the 
room. 

The loss of heat from buildings was first investi- 
gated both experimentalh' and theoretically by 
Peclet. The greater part of his work is given in 
Box's treatise en Heat. The results obtained by 
Peclet are difificult to apply practically and nearly 
all the rules that are used to determine the loss of 
heat from a building are largely empirical. The con- 
stants determined by the German government are 
probably the most reliable we have. They are given 
in the following table, the results being expressed 
in the heat units transmitted per square foot of sur- 
face per degree difiference of temperature. 

It is found that the thickness of glass in the win- 
dow makes a difiference in the heat transmission. 
Plate glass transmits about 30 per cent less than 
single glass, but this is only approximate. In the 
table below double glass refers to two sheets of 



Notes ox Heating and Ventilation 27 

glass with an air space between, what is sometimes 
called double glazing. Where brick walls are made 
double with air space between the air space will re- 
duce the loss of heat about 20 per cent below that 
given by a solid wall. 

The heat losses given in the following table 
should be increased as follows : Where the room 
has a north exposure and the 
winds are severe, add 10 per Factors for 

cent. \Mien the building is Exposure. 

heated in the day time only and 
allowed to cool during the night, add 10 per cent. 
When the building is heated occasionally — for ex- 



Table IV — Heat Losses. 



SuKFACt:. B T. U per h 1" r per sq ft. per degree 

difference of t mperature. 

Window, single glass 1.03 

Window, double glass 518 

Skylight, single glass 1.118 

Sljylight. double glass G21 

Brick wall 4 inches thick 68 

Brick wall 8 inches thick 46 

Brick wall 12 inches thick 32 

Brick wall IG inches thick 26 

Brick wall 20 inches thick 23 

Outer doors 42 

Floors, wooden beams, planked 083 

Floors, fireproof, floored with wood .124 

Ceilings, wooden beams, planked 104 

Ceilings, fireproof construction 14.5 

Ordinary wooden house construction 25 



ample, a church — add from 40 to 50 per cent. A\'here 
a room has a northerly exposure and is subjected to 
extremely high winds, add 30 per cent. It is usually 
advisable to assume for un warmed spaces, such as 



28 Notes on Heating and Ventilation 

cellars and attics, a temperature of about 32°. For 
vestibules and entrances unheated, which are being 
frequently opened to the outer air, a temperature of 
20° may be assumed. 

In determining the loss of heat from a building all 
surfaces should be considered which have on the 

side opposite the room a lower 

Determination of temperature than the tempera- 

the Loss of Heat 4. • ^u rr 

c ojuoo ui xicetu ^^^^^ j^ ^YiQ room. If a room is 

From a Build- . , . ^ , 

J situated over a portion of the 

cellar which is not heated, the 
loss of heat through the floor 
should be considered. If the room has over it an 
unheated attic the loss through the ceiling should 
be considered. The loss through the sides of a room 
which is surrounded by rooms at the same tempera- 
ture may be neglected. Doors entering directly into 
a room are considered to lose the same amount of 
heat as the windows. 

A common rule for the loss of heat from a build- 
ing is that given by Professor R. C. Carpenter in 

his book on ''Heating and Ven- 

Rules for Deter- tilation.'' This rule is developed 

mining the Loss from the following considera- 

of Heat. tion. Referring to Table I\\, 

we notice that one square foot 

of glass conducts approximately four times as much 

heat as a brick wall 20 inches thick. If, then, we 

divide the wall surface by 4, the result will give us 



Notes ox Heating and Ventilation 29 

the number of square feet of glass surface, which 
would lose the same quantity of heat. Adding to 
this the actual glass surface would give us the total 
equivalent glass surface. In addition to this heat 
transmitted through the walls we must add the heat 
which is lost by the air which passes directly through 
the walls themselves. It is assumed that for ordinary 
sized rooms the air in the room will be changed 
about once an hour, so that we must figure on heat- 
ing the entire air in the room about once per hour. 
One cubic foot of air w^eighs, approximately, 1/13 
of a pound. To raise a pound of air one degree re- 
quires .238 B. T. U.'s. Then to raise one cubic foot 
of air one degree would require .238xi/i3=.oi83 B. 
T. U. or one heat unit will heat 1-^.0183=54.6 cubic 
feet, or in round numbers say 55. If, then, we di- 
vide the contents of a room by 55 we will have the 
heat lost by filtration through the walls. Adding 
these factors together will give the total heat lost 
from the room. This rule may be expressed more 
concisely as follows : 

Rule i. — Divide the contents of the room by f^f^; 
add the glass surface and to this the zcall surface 
divided by 4. The sum zvill be the heat lost from 
the room per degree dUTerence of temperature be- 
tzveen the air in the room and the air outside 
the room. Multiply this sum by the difference in 
temperature between the air inside the room ^ and 



30 Notes on Heating and Ventilation 

that outside of the room and the product zuill be 
the heat lost from the room. 

This rule can be expressed algebraically as fol- 
lows : 

Let C represent tlie vohimc of the room, W the 
wall surface, G the glass surface and d the differ- 
ence of temperature betzveen the air outside and the 
air inside the room. The heat loss from the room 
per hour expressed in B. T. U.'s would be 
^ On W ] 

\ i- G d zvhere n is a factor which 

.55 4 j 

depends upon the tightness of the room and varies 

in value from i — j. For ordinary room n^=i, for 

corridors i.j, for vestibides 2 to j. 

It is quite customary to assume the difference in 
temperature between the air in a room and the air 
outside to be 70°. Where the windows are poorly 
fitted or the house loosely built the loss by filtra- 
tion should be doubled, and in halls where the doors 
are being opened and closed frequently this should 
be multiplied by three. 

There is one criticism on this method of figuring 
the heat lost in the room. The diffusion loss is as- 
sumed to depend upon the cubic contents of the 
room. This of course is manifestly not correct, as 
the diffusion loss occurs through the w-alls and 
windows and must depend upon the area of the 
walls and windows. The rule, however, will work 



Notes on Heating and Ventilation ^i 

very well for rooms of average size, but where rlie 
rooms have excessive wall and window surfaces, or 
where the cubic contents of the room is large com_- 
pared to the wall and window surfaces, this rule 
will give inconsistent results. The following rule 
seems to the author to be capable of a much wider 
application : 

Rule 2. — Diz'idc tlie zcall surface by 4; add the 
glass surface; multiply this sum by the difference in 
temperature between the air in the room and the air 
outside J and then multiply the result by iy2. This 
rule is for a zvell constructed building. If the build- 
ing is. old and poorly built, then instead of multiply- 
ing by iy2 the result should be multiplied by 2; en- 
trance halls multiplied by ^}4. 

This rule may be expressed algebraically as fol- 
lows : 

Let W represent the zcall surface, G the glass 
surface and d the difference of temperature betzveen 
the air outside and the air inside the room. Then 
the heat loss from the room per hour expressed in 

W 
^+G 



B. T. U.'s zvould be 



d n, zi'here n is a 



factor zi'hich depends upon the construction of the 
house or location of the room and varies in value 
from 7.5 to 2.j as stated above. 

In figuring the radiating surface for any room 
the cubic contents should alwavs be taken into con- 



32 Notes on Heating and Ventilation 

sicleration. In a large room with a small exposed 
wall surface, if only enough radiation is put in to 
cover the loss from walls and windows, the room 
w^ill be slow^ to heat. In addition. to taking care of 
the loss from w^alls and windows it is necessary for 
the radiator to heat the air in the room itself. In 
order to do this a large proportion of this air must 
either pass through the heating device or be car- 
ried out by the ventilating flues, so that where the 
cubic contents of a room is large it is advisable to 
add from lo to 20 per cent to the radiating sur- 
face to allow for the heating of the air in the room 
itself. The above remark applies only when the 
building is intermittently heated ; wdien the building 
is continuously heated it is not necessary to consider 
the volume of the room. 

The following temperatures are usually assumed 
in determining the heat losses : 



Table V — Temperatures Assumed in Heating. 

Degrees 

Temperature lof the outside air 

Temperature of stores 68 

Temperature of residences 70 

Temperature of halls and auditoriums 64 

Temperature of prisons 68 

Temperature of factories 60 to 68 

Temperature of cellars not warmed 32 

Temperature of attics not warmed 32 

Temperature of outside entrances 20 



The average temperature for the period of the 
year during which buildings are heated throughout 



Notes on Heating and Ventilation ^3 

the Central States may be assumed to be approxi- 
mately 35°. 

The following examples will show the method 
to be pursued in determining the heat lost from a 
building. 

Suppose a room, as shown in Fig. 4. Let the 
temperature be maintained in the room at 70 de- 
grees, the temperature of the 
outside air be o. Let the walls Example 1. 

be of brick 8 inches thick, plas- 
tered on the inside, the windows be 2^x6 feet, 
the ceiling of the room be 10 feet high. Let the 
room be on the second floor of the building, the 
rooms above and below heated. The window sur- 
faces are 2x2^x6=30 square feet. The total wall 
surface is 20x10=200 square feet. The net wall 
surface is 200 — 30=170 square feet. Then the heat 
lost from the room per degree difference of tem- 
perature by rule 2 would be i7CK-4-f- 30=72 J/^. As 
the difiference between the outside and inside tem- 
perature is 70°, the total heat lost is 72^x70=5075 
B. T. U. per hour. 

Take the same room as in Example i, except that 
the room is covered by a flat tin roof. The air 
space between the ceiling of the 
room and roof should be as- Example 2. 
sumed to be at a temperature of 
32°. Then, in addition to the loss figured in Ex- 
ample I, there will have to be added the loss due to 



34 Notes on Heating and Ventilation 



o' 




Figure 4. 



the tin roof. The area of the ceiHng of the room 
would he 14x20=280 square feet. Referring to 
Tahle R' we find the loss per hour through ceilings 



Notes ox Heating and Ventilation 35 

of wooden construction to be .104 B. T. U.'s per 
degree difference of temperature ; then the loss 
through this ceihng would be, per degree of temper- 
ature, .104x280-— 29.1 B. T. U.'s. The room being 
at 70° and the attic space 32°, the difference in tem- 
perature would be 70 — 32=38 degrees. The total 
loss through the ceiling would then be 29.1x38= 
1 105.8 B. T. U.'s. Adding this to the loss found in 
Example i we have a total loss from the room, 
5,075+1 io5.=6i8o B. T. U.'s. 



CHAPTER II , 



DIFFERENT FORMS OF HEATING. 

The dififerent heating systems may be classed 

under two general heads — Direct and Indirect. In 

direct heating the heating sur- 
Classification of . i i • i 

-_ ^. . . faces are placed m the rooms to 

Heating Apparatus. ^ 

be heated, as, for instance, 
stoves, steam radiators or hot water radiators. In 
indirect heating systems the heating apparatus is 
usually placed in some other room and the heat 
carried to the room to be heated by means of pipes. 
Under this head would be included hot air furnaces 
and the various systems of heating in which fresh 
cold air is made to pass over steam or hot water 
radiators on its way to the room. 

The indirect systems of heating naturally divide 
themselves into two other classes, those using nat- 
ural draft and those using forced draft. A good 
example of natural draft indirect heating is the hot 
air furnace, where the circulation of air through 
the house is produced by the difference in tempera- 
ture between the air in the hot air flues and the 
cold air outside the flues. The fan systems of heat- 
ing, used in heating school buildings and churches, 
are good examples of the forced draft system. In 



Notes ox Heating and Ventilation 37 

this case the draft is largely produced by mechanical 
means, usually a disc fan or a pressure blower. 

In order to understand better a discussion of the 
various forms of heating which will come later, it is 
desirable to understand in general the advantages 
and disadvantages of the various forms of heat- 
ing. 

The most primitive form of heating apparatus is 
the grate. In the grate the air which passes through 
the fire and is heated by the fire 
all passes up the chimney and Grates. 

only the heat given off by radia- 
tion to the walls and objects in the room is effective 
in heating the room. In grates of better construc- 
tion this is somewhat improved by surrounding the 
grate by fire brick so arranged that the brick will 
become highly heated and radiate heat to the room. 
But the fact that all the air heated by the grate 
passes up the stack makes this a very uneconomical 
form of heating. In the best form of open' grates 
only about 20 per cent of the heat of the fuel is 
eff'ective in heating the room. This form of heating, 
however, has been defended by many. It is a very 
popular form of heating throughout England and 
Scotland. The feeling of a grate-heated room is 
quite dift'erent from that of a room heated by other 
systems. All the heat is given off by radiation and 
the air in a grate-heated room is at a considerably 
lower temperature than the objects and persons in 



'^8 Notes on Heating and VentiLxVpion 

the room, owing to the fact that radiated heat does 
not h.eat the air through which it passes. The air 
of the room being at a lower temperature, its ca- 
pacity for moisture is not increased as much as it 
w^ould be were the air heated to a higher tempera- 
ture. The result is that the air contains propor- 
tionally more moisture than is the case in other 
forms of heating. This, no doubt, is an advantage. 
On the other hand it is impossible to heat the room 
uniformly, and a person is hot or cold, depending 
upon his distance from the grate. Heating by means 
of grates is practiced only in the more moderate 
climates. The grate is useful in houses heated by 
other forms of heating, as it serves as a most 
efficient foul air flue. The introduction of a large 
number of grates into a house adds materially to 
the ease with wdiich the house may be ventilated. 
The stove is a marked improvement over the grate 
as a form of heating, particularly from the stand- 
point of economy. The modern 
Stoves. base burner stove is one of the 

most economic and efficient 
forms of heating, making use of from 70 to 80 
per cent of the heat in the fuel. In heating by a 
stove the heat is given ofif both by radiation and by 
convection. The hot surface of the stove being at 
a higher temperature than the surrounding objects 
in the room, radiates its heat directly to these ob- 
jects. In addition the air surrounding the stove is 



Notes ox Heating and Ventilation , 39 

heated and rises, passing along the ceihng to the 
cold wall and window surfaces where it is cooled, 
drops to the floor and passes along the floor back 
to the stove to be again heated. In selecting a stove 
to heat a given room care should be taken to select 
one of ample size so that only in the coldest weather 
w^juld it be necessary to crowd it ; that is, keep on 
the drafts in order to heat the room. At the present 
time the stove as a general source of heat is being 
rapidly discarded because of the attendance re- 
quired, the space occupied and the unsightly ap- 
pearance of the stove. Another serious objection 
to the stove is the fact that it does not furnish venti- 
lation to the room which it heats. 

The hot air furnace is a natural outgrowth of 
the stove. In this system one large stove is placed 
in the basem.ent of the building, 

the air is taken from the outside, 

^ naces. 

passed over the surfaces of the 
stove or furnace, carried up through the flues to the 
rooms to be heated. The principal advantage of the 
hot air furnace is that it provides a cheap method 
of furnishing both heat and ventilation, it requires 
little attendance and does not deteriorate rapidly 
when properly taken care of. (The greatest disad- 
vantage of this system is in the fact that the circu- 
lation of the heated air depends entirely upon nat- 
ural draft ; that is, it depends upon the difference 
in weight between the air inside the flue and the air 



40 Notes on Heating and Ventilation 

outside the flues. This difiference of weight is ex- 
tremely small, so that the force producing circula- 
tion in the flue is always small. This force is easily 
overcome either by the winds or by the resistance 
of the piping. When a very strong wind blows 
against one side of the house it is difficult to heat 
the rooms on that side of the house. If the system 
is carefully designed, however, this difficulty can be 
overcome in a measure. Another serious objection 
to the hot air furnace is that it is seldom dust tight 
and dust and ashes are carried into the room. In 
general, how^ever, the hot air furnace may be con- 
sidered as a very good type of heating plant for 
small residences. 

In the case of the hot air furnace the heat is 
carried to the room by convection, as all heat is 
carried fromi the furnace by the air which passes 
around the furnace and enters the rooms from the 
flues. This air circulates in the room and heats the 
objects and air in the room. The efficiency of the 
hot air system will vary, depending on the relative 
proportion of the air taken from outside and upon 
the temperature of the air entering the room. If 
the cold air entering the furnace is taken from the 
house itself and not from outside the efficiency of 
the hot air furnace will be almost the same as that 
of a steam furnace ; that is, from 70 to 75 per cent 
of the heat of the coal will go into the rooms. If, 
however, the cold air is taken from outside, then 



Notes on Heating and Ventilation 41 

the heat used in heating the air from the tempera- 
ture of the outside air to the temperature of the 
room will be lost, and under ordinary conditions of 
operation the efficiency would be from 50 to 60 per 
cent. 

From the standpoint of ventilation direct steam 
heat has little advantage over a stove, as it 

gives no means of supplving 

. , . -r^ . ' , Steam Heating, 

iresh air. its use m g-eneral ^. 

^ Direct. 

should be confined to rooms 
which require little or no ventilation. Mechanically, 
however, it has many advantages over the stove or 
the hot air furnace. The boiler for a building hav- 
ing this form of heating can be located anywhere 
in the basement, and the rooms are free from dirt 
or gas. The modern radiator is easily adapted to 
almost any location in the room, it is not affected 
by w^ind or local conditions, and a distant room may 
be heated as easily as one close to the furnace. The 
efficiency of the direct steam heating system is about 
the same as that of a stove, and with a well-installed 
plant from 70 to 80 per cent of the heat of the fuel 
will be delivered by the radiator to the room. 

The application of direct hot water radiators as a 
method of heating is similar to that of steam, 
with the exception that the sur- 
faces are at a much lower tem- Hot Water, Direct. 
perature and hence more radi- 
ating surface will be required. It has an advan- 



42 Notes on Heating and Ventilation 

tage over steam in that the temperature of the heat- 
ing surface can be controlled easily, and can be any- 
where from the temperature of the room to 200 
degrees, hi the steam radiator the surface is usually 
not less than 212 degrees. The principal disad- 
vantage of this system is in the fact that the circu- 
lation of the system is by natural circulation ; that 
is, the circulation is produced by a difference in 
weight between the water in the hot leg of the 
system and in the cold leg of the system. This dif- 
ference in temperature is usually about 10 degrees, 
so that the dift'erence in weight betw^een these two 
cohniins of water is small and the resulting force 
producing circulation is, of course, small. It is 
necessary to be very careful in designing* the piping 
for the hot water system, as the circulation may be 
easily affected by resistance of the pipe. In addition 
it will be aft'ected by the height of the radiator 
above the boiler ; the greater the height above the 
boiler, the greater will be the difference in weight 
between the two columns of water and the stronger 
w^ill be the force producing circulation.' This sys- 
tem in general requires more careful design and 
construction than the steam system. The efficiency 
of the hot water system is practically the same as 
that of steam, and we may expect to obtain in the 
room from 70 to 80 per cent of the heat in the 
coal. 

In heating with indirect steam radiation cold air 



XoTES OX Heating and V'entilation 4 



o 



is drawn from the outside, passed through and 

around the hot radiator, which is 

., •. . 1 • .1 1 ^ Indirect Steam 

usually situated ui the basement, „ . . 

' Heating. 

and delivered by pipes to the 
rooms to be heated. The rules governing the intro- 
duction of air mto the rooms and the method of 
running pipes is similar to that employed 
with hot air furnaces. The principal advantages 
of indirect steam over hot air are : Each room has 
a separate source of heat, the system is not afifected 
by the winds and no dust or obnoxious gases are 
carried to the rooms. 

The air entering the room will always be as 
pure as the air which furnishes the source of sup- 
ply. The source of heat being independent of the 
position of the boiler, it is possible to place the 
indirect radiator anywhere in the building and long 
hot air pipes are not necessary. This makes the 
indirect radiator much more efficient and more cer- 
tain in operation than the hot air ftirnace. The 
efficiency of this system, from the standpoint of coal 
consumption, will be much less than in direct forms 
of heating and about the same as the hot air fur- 
nace ; that is, from 50 to 60 per cent of the heat of 
the coal will be used effectively in heating. 

The application of hot water 
. ,.,..., , - Indirect Hat 

indirect is similar to that of water Heating. 

steam and the efficiency is prac- 
tically the same. The use of hot water indirects has 



•14 NoTKs ON 11katii\(; and Vkntilation 

hocii nuicli more liiuitod than the use of steam indi- 
rocts. The installation of hot water indirects must 
he (lone with i;reat care so that each radiator will at 
all times have the proper amount (^f hot water circu- 
lating; throui^h it. In ihe hot water indirect radi- 
ators, if for any reason the water in <he radiator 
becomes cooled, the radiator will be in dan^^er of 
freezini;-. In mild climates this difiiculty would not 
be as serious as in locations where the weather is 
extremely cold. 

in buil(lini;s of a public or semi-public character, 
where a lari^e number of people are to be assembled 

in a relatively small space, it is 
Fan System of ' • i i 

J-. .. necessary to provide adequate 

ventilation. In the systems that 
have been previously described it is impossible to 
introduce into the room sufficient (piantities of air 
to ventilate the rooms j)roperly. It may be said in 
general tliat^nc^ system of natural circulation has 
ever produced satisfactory ventilation in a room oc- 
cupied by a larj^e number of people; it is necessary 
to provide some means of mechanically circulatint; 
the air. Tliis is done in the fan svstem bv means 
of a |)ressure blower or a disc fan. 

In the fan system the pressure produced by the 
fan makes the circulation so positive that it is not 
affected by winds ov bv the distance of the room 
from the fan itself. The air is taken from the out- 



Notes on Heating and Ventilation 45 

side, passed through the heating coils and forced 
into the building by the fan. 

There are two general methods of heating and 
ventilating with the fan system. In one system the 
air is first passed through a tempering coil, then 
taken by the fan and delivered through a heating 
coil. Each room has a connection both to the hot 
air and to the tempered air chamber. The tem- 
perature of the air in the room is adjusted by tak- 
ing the air either from the hot air chamber or from 
the tempered air chamber. In the second system 
the rooms themselves are heated by means of direct 
radiation and the fan delivers air to the rooms only 
for the purpose of ventilation. In this case no heat- 
ing coils would be necessary. 

In the first method the economy of the system is 
low, as owing to the large amount of air required 
for ventilation the quantity of air introduced into 
the room is ordinarily greater than is necessary for 
the purpose of heating the room. The economy of 
this form of fan system depends very largely upon 
the amount of air necessary, but in most cases its 
efficiency would not exceed from 40 to 50 per cent ; 
that is, only 40 to 50 per cent of the heat units in the 
coal would be effective in heating. In the combined 
fan system, where direct radiation is used for heat- 
ing and the fan system for ventilation, the economy 
of the system is better, probably from 50 to 60 per 
cent. 



46 Notes on Heating and Ventilation 

The increase in economy of this system is due to 
the fact that it is necessary to run the fans only 
when it is necessary to ventilate the building. 

In addition to the combination just described, of 
direct radiation and fan ventilation, there have been 

Combination of devised innumerable combina- 

Dlfferent Sys- tions, combinations of direct 
terns. and indirect steam, direct and 

indirect water, water and hot air, steam and hot 
air. Probably the combinations which have been 
most used have been combinations of direct and 
indirect steam and the combinations of hot water 
and hot air. 

The economy of any heating system depends upon 

the completeness with which the coal in the furnace 

is burned and the heat lost by 

The Economy of , . . , . .. ^. 

^.«, 4. o i. the clinnnev and the ventilatmp' 

Different Systems. -, ^ 

flues. If, with each of the above 
systems the coal was completely burned and all the 
heat given ofif were used, then each one of the sys- 
tems would have perfect efficiency. 

The losses from, any system, given in detail, are as 
follows : Loss through imperfect conihiistion of 
coal, through the escape of hot gases up the chimney 
and the loss of heat in the air passing up the venti- 
lating^ -flue. 

If the furnace is properly constructed and insures 
good combustion, the loss due to imperfect com- 
bustion is small. The loss of heat passing up the 



Notes ox Heatixg and Ventilation 47 

cliimney will depend upon the temperature at which 
the gases leave the chimney and the amount of air 
used to burn a pound of coal. The loss by the venti- 
lating flue will depend upon the amount of air it is 
necessary to supply to the rooms for ventilation. 

If the hot gases leave the heating apparatus 
at the same temperature and the same amount 
of air is used for ventilation, then the ef- 
ficiency of each system wdll be practically the 
same. If the rooms are not ventilated, then, of 
course, the loss due to the heat passing up the 
ventilating flues will be saved and the system will 
be more economical. In fact, strictly speaking, the 
loss by ventilation should not be considered as enter- 
ing into the efticiency of the system. This loss is 
entirely independent of the system used and depends 
entirely upon the amount of air which must be sup- 
plied for purpose of ventilation. It is quite obvious 
that any system involving ventilation wdll require a 
greater amount of coal. The loss due to ventilation 
is due to the fact that all the heat which is given to 
the air between the temperature of the air outside 
the building and the air in the room is ineffective in 
heating and is lost up the ventilating flues. It w^ould 
be poor policy, how^ever, for the designers of heat- 
ing systems to cut down the amount of ventilation 
in a room in order to save coal. In several States 
there are general State laws which require that a 
certain amount of air be furnished each person per 



48 Notes on Heating and Ventilation 

hour in school buildings and other buildings of a 
public character. The necessity and importance of 
ventilation will be discussed under another head. 



I 



CHAPTER III. 

THE DESIGN OF A DIRECT STEAM-HEATING 

SYSTEM. 

Steam heating is usually done by direct or by 
indirect radiation or by combination of both direct 
and indirect radiation. In small residences occupied 
by only three or four persons it is customary to use 
only direct radiation. The practice, however, is a 
questionable one, and it seems desirable, even in 
small residences, that some indirect radiation be used 
so as to provide a means of ventilation. Often- 
times only one indirect radiator is used, bringing its 
air either into the room most used or into the main 
hall so that it may be distributed throughout the 
house. In factories and office buildings where a 
large amount of air is introduced by the opening 
and closnig of doors it is customary to use only 
direct radiation, and in such buildings this is per- 
missible. 

In order to understand thoroughly the operation 

of a steam heating system the nature and properties 

of steam should be studied. 

o, . , , Nature and Prop- 

Steam is a watery vapor, and as ^^.^^ ^^ ^^^^^ 

used in ordinary radiator prac- 
tice always contains a certain amount of water in 
suspension, as does the atmosphere in foggy 
weather. 



50 Notes on Heating and V^entilation 

When water is heated in a steam boiler the tem- 
perature is slowly increased from the initial tem- 
perature of the water to the temperature of the 
boiling point. When the water reaches the boiling 
point small particles of the water are changed from 
water to steam, rise through the mass of water and 
escape to the surface ; the water is then said to boil. 
The temperature at which the water boils depends 
entirely upon the pressure in the boiler and ob- 
viously, as the boiling point increases more and 
more, heat is required to produce steam. 

Take, for instance, a given case. Suppose we 
start with water in the boiler at 40 degrees and 
the pressure in the boiler at atmospheric pressure, 
that is, 14.7 pounds. Under this condition it will 
be necessary to increase the temperature of the 
water in the boiler to 212 degrees, at which point 
w^ater will commence to boil. It will be necessary 
to add 212 — 40=172 B. T. U's for every pound of 
water in the boiler. In order to convert all the 
water into steam it will be necessary to supply 
965.7 heat units for each pound, in addition to the 
172 heat units consumed in raising the water to the 
boiling point. During the operation of boiling, 
however, the temperature of the water remains con- 
stant and the 965 heat units added in order to 
change the water at the temperature of the boiling 
point into steam are consumed in separating the 
molecules of water and changing the water from a 



Notes on Heating and Veij,tilation 51 

liquid into a gas. This last quantity is termed the 
latent heat and it is the latent heat of water which 
is used primarily in furnishing heat to the room in 
steam heating. As the pressure in the boiler in- 
creases the latent heat diminishes. The relation of 
these various quantities has been very carefully de- 
termined by Regnault and compiled in the form of 
steam tables. The following is an abbreviated steam 
table. More complete tables will be found in Pea- 
body's Steam Tables, or in any of the mechanical 
engineering handbooks. 

STEAM TABLES. 

Column I of the Steam Table gives the pressure 
of the steam above the atmosphere in pounds per 
square inch and below the atmosphere in inches of 
mercury. Column 2 gives the corresponding tem- 
perature of the steam. Column 3 gives the heat of 
the liquid or the heat necessary to raise one pound 
of water from 32 degrees to the boiling point, cor- 
responding to the pressure. Column 4 gives the 
latent heat necessary to change a pound of water 
at the temperature of the boiling point into steam 
at the same temperature. Column 5 is the sum of 
columns 3 and 4, and represents the amount of 
heat necessary to raise a pound of water from 32° 
to the boiling point and then change it into steam 
at the temperature of the boiling point. The quan- 
tities given in this column are called total heat. 





Table VI. — Properties of Steam. 




Pressure 


Tempera- 


Heat of 


Latent 


Total 


Volume of 
1 lb. of 


or vacuum 


ture 


the Liquid 


Heat 


Heat 


steam 


Inches 




• 








mercury 












-24 


137 


105 


1019 


1124 


135 


20 


160 


128 


1003 


1131 


78.3 


16 


175 


143 


992 


1135 


55.9 


14 


187 


155 


984 


1139 


43.6 


8 


197 


165 


977 


1142 


35.8 


2 


205 


173 


971 


1144 


30.6 


Pounds 












per sq. in. 















212 


180.9 


965.7 


1146.6 


26.86 


1 


215 


184 


964 


1148 


25 


2 


219 


188 • 


961 


1149 


23 


3 


222 


191 


959 


1150 


22.3 


4 


224 


193 


957 


1150.5 


21.2 


5 


227 


196 


955 


1151 


20.16 


10 


239 


208 


946 


1154 


16.3 


15 


249 


218.8 


939.-3 


1158.1 


13.7 


20 


258.7 


228 


932.5 


1161 


11.85 


25 


266.7 


236.2 


927.1 


1168.3 


10.36 


30 


273.9 


248.5 


922 


1165.5 


9.34 


35 


280.5 


250.2 


917.3 


1167.5 


8.45 


40 


286.5 


256.3 


918 


1169.3 


7.73 


45 


292.2 


262.1 


909 


1171.1 


7.11 


50 


297.5 


267.5 


905.2 


1172.7 


6.61 


55 


302.4 


272.6 


901.6 


1174.2 


6.16 


60 


807.1 


277.2 


898.4 


1175.6 


5.77 


65 


311 5 


281.8 


895.1 


1176.9 


5.48 


70 


315.8 


286.1 


892.1 


1178.2 


5.13 


75 


319.8 


290.8 


889.1 


1179.4 


4.86 


80 


328.7 


294.3 


886.3 


1180.6 


4.63 


85 


327.4 


298.1 


888.6 


1181.7 


4.41 


90 


330.9 


301.8 


881 


1182.8 


4.20 


95 


334.4 


305.4 


878.5 


1183.9 


4.02 


100 


337.6 


308.9 


876 


1184.9 


8.83 


110 


343.9 


315.4 


871.4 


1186.8 


3.57 


120 


349.8 


321.5 


867.1 


1188 6 


3.38 


130 


355 


327.5 


868 


1190.3 


3.1 


140 


360 


888.5 


859.1 


1191.9 


2.92 


150 


365.7 


338.3 


855.4 


1193.4 


2.75 



Notes on Heating and Ventilation ^3 

Column 6 gives the volume of one pound of steam 
at the different pressures. 

EXAMPLES IN USE OF STEAM TABLE. 

Example i. — It is required to convert lo pounds 
of water at ^2° into steam at 100 pounds gauge 
pressure. 

Solution. — We see from column 5 that the total 
heat of I pound of steam at 100 pounds pressure 
is 1,184.9 heat units. Then to form 10 pounds of 
steam would require 10 times this amount, or 
11,849 heat units. 

2. How many heat units will be required to 
form 5 pounds of steam from feed water at 100° 
in temperature into steam at 10 pounds gauge 
pressure ? 

Solution. — The total heat of steam at 10 pounds 
pressure above 32° is 1,154 heat units. In this 
case the feed water already contains in it above 2^"" y 
100 — 32=68 heat units. The specific heat of water 
being i, the heat units required to form a pound 
of steam will be 1,154 — 68=1,086, and to form 5 
pounds of steam would require 5X1,086=5,430. 

3. A steam pipe is 8 inches in diameter. The 
pressure of steam in the pipe is 10 pounds gauge. 
The steam pipe is to transmit 1,600 pounds of steam 
per hour. What will be the velocity of steam in the 
pipe ? 

Solution. — From column 6 of the table we see 
that the volume of i pound of steam at 10 



54 Notes on Heating and Ventilation 

pounds gauge pressure is 16.3 cubic feet. Then 

1,600X16.3=26,080 cubic feet, the volume of steam 

passing per hour. This divided by 3,600 equals y2, 

the number of cubic feet passing per second. An 

8-inch pipe has an area of 50 square inches ; 

5o-f-i44=.347 square feet; 72-f-.347=2o8 feet per 

second, which represents the velocity of the steam 

passing through the pipe. This velocity is very 

high. Ordinarily the velocity in steam pipes should 

not exceed 100 feet per second, even in very large 

pipes. 

LOSS OF HEAT FROM RADIATORS. 

In designing a direct steam system it will be nec- 
essary first to compute the heat losses from the 
various rooms by the rules previously given. After 
these losses are determined it will be necessary to 
place sufficient radiating surface in the room to 
supply these losses. In order to know the amount 
of surface that should be placed in a room it is 
necessary to know the amount of heat given off per 
square foot by the different forms of radiators. 
Heat losses for the different forms of direct radi- 
ators are given in the following table: 

Column 5 is the column which shows the relative 
effectiveness of the various types of radiators. It 
is obtained in the following manner : Take, for ex- 
ample, the two-column cast iron radiators, results of 
which are given in line 2 of the table. A pound of 
steam at 226°, as we see from the steam tables. 



Notes on Heating and Ventilation ^^ 

gives up its latent heat in condensing which amounts 
to 965 heat units. This radiator condensed .265 
pounds of steam per square foot of surface per 
hour. Then 965X.265=255.7, the heat units given 



Table VII — Loss from Wrought Iron Pipe 


and 






Cast Iron Radiators. 








i-i 




u. 




B -^^ 




5*: 





c 


"SS 


- E 


O*^ 


C7 


•^Se 


'•5 


^ l- 


a. 5 


O o 
<11 ^ 


E wi i- 


(A 


fci5! 2 


WJ 


. 


3 Ti 


<u 


nl u- ? 


a> 


^ 4^_I 




o2 


(u.t: 


J- 0) 

2 c 
0).= 


bs ste, 
sed pe 
per ho 




1- o T3 
<li "^ C 

3EE 


a 
>» 


d 




i^ 


03 


per ho 
of te 
stea 




CAST IRON RADIATORS, 


38 INCHES. 






1 column. 


..48 sq.ft. 


226 


105 


.212 




1.82 


2 column. 


..48 sq.ft. 


226 


76 


.265 




1.70 


3 column. 


..45.3 sq.ft. 


226 


88 


.204 




1.42 


6 column. 


..36 sq.ft. 


225 


71 


.217 




1.35 




WROUGHT IRON 


RADIATORS^ 38 


INCHES. 






1 column. 


.12 sq.ft. 


221 


89 


.446 




3.27 


2 column. 


.42 sq.ft. 


222 


83 


.284 




2. 


3 column. 


.48 sq.ft. 


229 


70 f 


.294 




1.77 


4 column. 


..48 sq.ft. 


226 


73 


.202 




1.27 


1" wall coil, 1 pipe high. 


212 


70 


.41 




2.8 


1" wall coil, 4 pipes high. 


228 


65 


.425 




2.48 



Up by the radiator per square foot per actual sur- 
face per hour. The steam in the radiator was at a 
temperature of 226° and the air in the room 
at a temperature of /6°, the difference in tempera- 
ture being 150°. If we divide 255.7 by 150 the 
result is approximately 1.7. This result represents 
the B. T. U's transmitted per square foot of rated 
surface per hour per degree difference of tern- 



^ Notes on Heating and Ventilation 

perature between the steam inside the radiator and 
the air in thvi room. This is the quantity which 
should be used in comparing the relative merits of 
the various forms of heating surfaces. 

The results of a series of experiments made at 
the University of Michigan, extending over a period 
of a number of years, together with the results 
show^n in the foregoing table, lead to the following 
conclusions : 

Radiators zvith different steam volumes do not 
give essentially different results, except as the vol- 
ume is so small as to restrict the passage of steam. 

Single column radiators, as shozcn in Fig. 5, 
usually shoiv larger results than those with more 
than ouc column. The condensation per square foot 
of radiator per degree difference of temperature as 
shown in column 5 of Table VII shows a rapid de- 
crease as the number of columns increases. The 
reason for this is quite apparent when we consider 

the position of the radiating sur- 

Diiferent Types faces in a single pipe radiator as 

of compared with the surface in a 

Relative Efficiency, three-pipe radiator. Referring 

to Fig. 6, tube B, you will note 
that this tube can radiate heat in all directions with- 
out interference, except those lines which radiate 
to columns A and C. Columns A and C being at 
the same temperature, no radiant heat passes be- 
tween them, so that all the surface of column B 




Fig. 5. Single-Column Cast Iron Radiator. 



^ Notes on Heating and Ventilation 

which would radiate its heat to columns A and C is 
unaffected. The amount of surface which does 
this, however, is extremely small. 

Suppose we take point i on column B. The heat 
from that point radiates in a straight line in all 
directions. But all the rays of heat between ray 2 
and ray 3 strike on column A and are lost because 
column A is the same temperature as column B. 
The number of rays that do this are extremely small 
in a single column radiator. 

If we consider column B in a three-column radi- 
ator and take point i on column B we see that all 
the rays between 2 and 3, 4 and 5, 6 and 7, 8 and 9, 
10 and II are lost and become ineffective for 
heating as columns A, C, D, E, F, are at the same 
temperature and intercept rays passing into the 
room. 

When the columns in a radiator have been in- 
creased from 5 to 6 then the inner columns have 
practically no effect in giving off radiant heat, and 
the only heat they give off is given by convection 
due to the passage of air through the radiator. 

In addition to the experiments given in the table 
a series of experiments were made on radiators 
painted dift'erent colors and on unpainted radiators. 
The results of these experiments seem to show that 
the painting of a radiator does not materially affect 
the heat given off by the radiator. 



Notes on Heating and Ventilation 



59 



By glancing at Fig. 6 we see that the greater the 
distance between the columns or pipes of a radiator 
the smaller would be the number of rays of radiant 
heat intercepted by other columns of the radiator 




O O 



d/ng^/e Co/i/ma 




boo 



o o 



poo 



r/?ree Co/c/m/?. 



Fig. 6. 

and the larger would be the radiating effect; the 
wider the space between the columns of the radi- 
ator the more effective does the radiator become in 
giving off heat. 



60 Notes on Heating and Ventilation 

The writer has had opportunity to make a series 
of tests on radiators of the two-column type, having 
the sections of one radiator spaced at 2^ inches 
and the sections of the other radiator 3^ inches. 
The increase of ^ inch in the length of space added 
approximately 10 per cent to the effectiveness of the 
radiator. 

Radiators are made in standard heights. The 
height most used is 38 inches. They can be pur- 
chased, however, in varying heights from 15 to 45 
inches. The radiators of various heights are rated 
at a certain number of square feet per section. For 
instance, a 38-inch two-column radiator, as shown 
in Fig. 7, is rated at 4 square feet per section. As 
a rule, however, radiators are slightly overrated. 
A radiator containing 48 square feet has an actual 
surface, when measured, of about 47 square feet 
in most two-column radia'tors. In some cases, par- 
ticularly in radiators having a large number of col- 
umns, the radiators are very much overrated. In 
one instance a radiator rated at 36 square feet had 
an actual surface of only 2^ square feet. In pur- 
chasing a radiator, therefore, it is important to 
know that it has approximately the surface given 
in the catalogue of the manufacturer, as the radi- 
ating power depends primarily upon the square feet 
of surface it contains. . 

Comparing lines 2 and 6 of Table VII you will 
notice that the two-column wrought iron radiator 




Fig. 7. Two-Column Cast Iron Radiator. 




Fig. 8. Three-Column Cast Iron Radiator. 




Fig. 9. Six-Column Cast Iron Radiator. 






End view of section. 



64 Notes on Heating and VENTILATIO^f 

transmits about lo per cent more heat than the 
two-column cast iron radiator. This is undoubtedly 
due not so much to the difference of material as to 
the difference in the spacing of the columns com- 
posing the radiators. Wrought iron pipe wall coil, 
as shown in the last line of the table, condenses 
almost twice as much steam as the cast iron ra- 
diator; in other words, it gives off about twice as 
much heat as the radiator. The reason for this is 
not so much the dift'erence in material as the differ- 
ence of location. In the case of the cast iron radi- 
ator the air at the base becomes heated, rises along 
the radiator, becoming more and more heated as it 
comes nearer to the top, so that at the top of the 
radiator there is little difference between the tem- 
perature of the air surrounding the radiator and 
the temperature of the radiator itself. This reduces 
the transmission of heat near the top of the radi- 
ator. In the wall coil, the sections being placed in 
a horizontal position, the air remains in contact with 
the coil for a short time only, so that the air sur- 
rounding all portions of the coil is practically at 
the same temperature. To state this in another 
way, in the cast iron radiator, with the sections 
placed vertically, the difference in temperature be- 
tween the air outside the radiator and the steam 
inside the radiator is much less than in the wall 
coil, where the pipes are placed horizontally, making 
the wall coil much more eft'ective per square foot of 



Notes on Heating and Ventilation 65 

surface. Approximately we can say that a wall coil 
will do twice as much per square foot as a cast 
iron radiator. Their extensive use, however, ex- 
cepting in shop buildings, is always more or less 
questionable, owing to their unsightly appearance 
and the difficulty of installation in many places. 

Besides the usual radiator in which a large pro- 
portion of the heat is given off by radiation and 
a smaller portion by convec- 
tion, there is what are known Flue Radiators. 
as flue radiators. In a flue 

radiator each section, as shown in Fig. lo, has a 
projecting flange at the outer edge, so that there is 
confined in the radiator itself a series of narrow hot 
air flues. In these radiators only the external sur- 



Table VIII — Heat Loss from Flue Radiators. 

A B 

1. Size of radiator 6 sec. 38" 6 sec. 38" 

2. Rated surface, square feet 42 42 

3. Actual surface, square feet 39 39.41 

4. Temperature steam 226 226.9 

5. Temperature external air 103.3 103.5 

6. Difference between steam and air.. 123 123.4 

7. Condensation per sq. ft. rated sur- 

face 1847 .1922 

8. B. T. U.'s per deg. diff. per sq. ft. 

rated surface 1.437 1.5 

9. Temperature of air entering flues. 106 102 

10. Temperature of air leaving flues.. 187 182 

11. Cubic feet of air leaving flues per 

minute 37.59 45.77 

12. Average velocity of air leaving, ft. 

per minute 150.3 171.3 

13. Percentage of heat transmitted by 

flues 36 41 

14. Percentage of heat radiated 64 59 




Fig. 10. Cast Iron Flue Radiator. 



Notes on Heating and Ventilation ^'^ 

face of the radiator acts as radiating surface. The 
interior surfaces of the radiator act as indirect 
radiators to heat the air which is drawn up from 
below the radiator. The heat losses from two well- 
known forms of flue radiators are given in Table 
VIII, which gives the loss by radiation from the 
radiator as separated from the loss due to the heat 
transmitted to the air in the flues. 

The action of the flue radiator depends upon the 
design of the flues. There should be no point of 
restricted flue area ; that is, the air should be given 
a free passage from the base of the radiator to the 
top. Flue radiators are particularly serviceable in 
rapidly circulating the air in the room and can be 
used in a large room having small window surfaces 
to assist in heating the air in the room more rapidly 
than is done by the ordinary radiator. The flue 
radiator is also used in connection with ventilation, 
in which case the base of the radiator is closed and 



Table 


IX- 


-Heat Transmission. 


Difference 


in 


B. T. 


U.'s transmitted 


temperature. 


per deg. diff. per hr. | 


80 






1.56 


90 






1.57 


100 






1.58 


110 






1.6 


3 20 






1.615 


130 






1.63 


140 






1.645 


150 






1.65 


160 






1.675 


170 






1.69 


180 






1.705 


100 






1.72 



68 Notes on Heating and Ventilation 

is connected with the outside air. This phase will 
be taken up more in detail under the head of Venti- 
lation. 

In the foregoing tables it has been assumed that 
the heat lost per degree of difference of temperature 

between the steam in the ra- 

Heat Lost from diator and the air outside the 

Radiators Under Vary- radiator was a constant quan- 

ing Temperatures. ^ tity. In general this may be 

assumed as true for the ordi- 
nary conditions under which radiators operate. 
Where radiators are operated on very high or very 
low temperatures there is a difference in the amount 
of heat transmitted per degree of difference of tem- 
perature. Table IX gives the heat transmitted for 
each degree difference of temperature -between the 
steam inside and the air outside the radiator per 
hour per squaje foot of surface for the two-column 
cast iron radiator 38 inches high. 

For ordinary conditions of operation — that is, 
when the steam is at a pressure from atmospheric 
to 10 pounds and the temperature of the room is 
70 degrees — there will be no necessity to consider 
this variation in the transmission of heat due to 
differences of temperature between the steam and 
the air. There are, however, conditions in drying- 
rooms that are to be kept at a very high tempera- 
ture, where this will make an appreciable difference 
in the amount of radiation to be used. In vacuum 



Notes on Heating and Ventilation 



69 



systems also, where a very low vacuum is carried, 
it would be necessary to take these factors into 
consideration. 

The following suggestions apply to the placing 
of radiators in the room. The radiators should be 
placed in the coldest portion of the room. In gen- 
eral it is best to place the ra- 
diators in front of the win- Installation of Direct 
dow, selecting a radiator of Radiators. 

such height that the top will 
be an inch or two below the window sill. There 



Fig. 11. 




are a number of advantages in placing the radiator 
in front of the window. Probably the most impor- 



70 Notes on Heating and Ventilation 

tant is the fact that it reduces the strong cold down 
draft along the window surfaces. 

Figure ii shows the effect upon the circulation 
of the air by placing the radiator in front of the 
windows. In this case we get two separate cur- 
rents of air. The current rising from the radiator 
divides, one current passing out into the room, 
being cooled by the wall surfaces and objects in 
the room, dropping down to the floor and passing 
back along the floor to the radiator ; the other cur- 
rent, passing directly to the cold wall surface, is 
cooled, drops down along this surface and comes 
back to the radiator, making the circulation along 
the cold walls and windows close to the radiator 
a local one which does not affect the occupants of 
the room. 

Carpets and rugs should not extend under the 
radiator. If a radiator is allowed to stand upon 
a carpet or rug for any great length of time, the 
heat from the legs of the radiator will eventually 
deteriorate the fabric of the rug. In a carpeted 
room the radiator may be placed upon a hardwood 
or a marble base. 

When radiators are placed next the wall a space 
of 13^ inches at least should be left for the circula- 
tion of air behind the radiator. 

Unless otherwise specified, radiators are usually 
tapped as in Table X. 



Notes on Heating and Ventilation '71 

The best method of figuring radiating surface is 
to determine the actual heat loss from the room in 
B. T. U's, then decide upon the form of radiator 
which you propose to use. 
Suppose, for example, that a Rules for Direct 
two-column cast iron radiator Heating, 

is selected. The steam pres- 
sure to be carried is 5 pounds. The temperature 
in the room is required to be 70 degrees. Referring 
to the table of heat losses from direct radiators 



Table X — Radiator Tappings. 

For one-pipe work radiatoi's containing — 

Inches. 

24 sq. ft. and under 1 

From 24 to 40 sq. ft 1^ 

From 40 to 100 sq. ft 1^2 

Above 100 sq. f t 2 

For two-pipe work radiators containing — 

48 sq. ft. and under. lx% 

From 48 to 96 sq. ft 1^x1 

Above 96 sq. ft. . iy2xli4 



(Table VII, we see that a two-column cast iron 
radiator loses 1.70 heat units per degree difference 
of temperature per square foot of rated surface per 
hour. The temperature corresponding to 5 pounds 
pressure of steam as given in Steam Table (Table 
VI), is 22y degrees, and the dift'erence between this 
and the temperature of the room will be 157 de- 
grees. Then the heat lost will be 1.70X157=266 
heat units per square foot per hour. Dividing the 
heat loss, as given by the rule for loss of heat, by 



72 Notes on Heating and Ventilation 

2.66 gives the the number of square feet of radi- 
ation to be used. 

This is the only method that can be used at all in 
rooms where conditions are exceptional. For rooms 
of ordinary construction, heated to 70 degrees, a 
large number of thumb rules are used. Some of 
these thumb rules are as follows: 

In the following rules the expression wall sur- 
face means exposed wall surface, that is, those sur- 
faces which have outside air temperature on one 
side and room temperature on the other side. 

Rule i. Divide the volume of the room by 35. 
Add one-fourth of the exposed ivall surface; add 
the glass surface, and multiply the sum of these 
three quantities by .2J3. The product will be the 
direct radiation in square feet. 

Rule 2. For ordinary rooms. Divide the ex- 
terior zvall surface by 4, add the glass surface and 
multiply the sum by .4. 

B. For entrance halls. Divide the exterior wall 
surface by 4, add the glass surface and multiply 
the sum by .34. 

C. For the Tca// surface in basement rooms be- 
long the ground line. Divide the 7call surface by 4 
and multiply the result by .//. 

D. For floors having unhealed space below. 
Divide the floor space by 4 and multiply the result 
by .23. 



Notes on Heating and Ventilation 73 

Rule 3. Divide the volume of the room in 
cubic feet by the factors given below and the quo- 
tient will be the radiating surface in square feet. 

First -floor rooms, one side exposed 55 

First floor rooms, two sides exposed ^0 

First floor rooms, three sides exposed. ... 45 

Sleeping rooms, second floor 60 to 70 

Halls and bath rooms ^0 

Offices 50 to y^ 

Factories and stores 75 to 1^0 

Assembly halls and churches 75 lo 1^0 

Rule 4. (Baldwin's Rule.) Divide the dif- 
ferences between the temperature at which the 
room is to be kept and that of the coldest outside 
temperature by the difference betzveen the tempera- 
ture of the steam in the radiator and that at which 
you wish to keep the room and the quotient will be 
the square feet of radiating surface to be allowed 
for each square foot of equivalent glass surface. 
By equivalent glass surface is meant the wall sur- 
face divided by 4 phis the glass surface. 

In all of these rules the factors to be allowed for 
exposure should be applied. These factors are 
given under the head of ''Factors for Exposure." 
Where the rule does not involve the contents of the 
room it will be necessary in very large rooms or in 
rooms where the wall surface is very small in pro- 
portion to the contents of the room, to add a cer- 




Fig. 12. 
BASEMExNT PLAN. 



(74) 



Notes on Hp:ating and Ventilation '75 

tain proportion of radiation, usually not more than 
20 per cent, to allow for heating the air in the 
room quickly when it has once been allowed to 
cool. 



Table XI- 


-Dimensions and Heat Iiosses. 










<v 


<D* 


* '^ 







« 





•^^ 


"^ 0. . 


• 


09 

a 

9> 


B 




«M 


0«M 

a 3 


' en ;r 





a 

Q 



> 


d en 


.^ 03 




Tarlor 


.13'9"xl2'9"x9'6" 


1665 


216 


36 


9450 


Sitting room. . . 


14'3"xl5'6"x0'0" 


2100 


95 


48 


7035 


Dining room. . . 


.12'6"xl3'9"x0'0" 


1640 


145 


36 


7350 


Kitchen 


. 13'0"xl3'0"x9'fr' 


1610 
1210 


249 
197 


36 
18 


10300 
7035 


Hall 


.12'0"xl0'0"x9'6" 




SECOND FLOOR. 








W. Chamber . . . 


.ll'6"xl3'6"x8'G" 


1320 


172 


48 


10050 


Alcove 


.10'0"x 9'frxS'O" 


810 


130 


40 


7560 


So. chamber. . . . 


.12'6"xl4'9"x8'6" 


1560 


172 


24 


7035 


N. chamber. . . . 


13' xl3' x8'f3" 


1440 


188 


24 


7455 


Bath 


.6' X 8' x8'6" 


410 


50 


18 


3150 


E. chamber. . . . 


.13' x 8' x8'6" 


880 


160 


18 


5250 


Front Hall. .. j 


14' X 4' x8'6" 


/ 885 


33 


18 


2730 


8' X 6' x8'6" 


S 









In order to understand better the methods of 
determining the heating surface required for a 
given house, it would be best to consider a concrete 
example. Figs. 12, 13 and 
14 represent the basement, Example. (Direct 
first and second floors of a Radiation.) 

residence. The house is con- 
structed of wood, sheathed, papered and clap- 
boarded on the outside and plastered on the inside. 
On the first floor the rooms are 9 feet 6 inches 
high and on the second floor 8 feet 6 inches high. 



Porch 




T 



Pi 



Vestibule 

I K— [-- 10-i---4 




Fig. 13. 
FIRST FLOOR. 



(76) 



Notes on Heating and Ventilation 'J'7 

The windows are 6 feet high and the standard size 
is 3 feet wide. Table XI gives the general dimen- 
sions of the room and the heat losses from the 
various rooms, assuming the temperature of the 
outside air to be zero and the temperature of the 
inside to be 70 degrees. 



Table XII — Results of Computation, Direct System 



First Floor. _ | OQ h 

Parlor 9450 

Sitting room ...:..... 7035 

Dining room 7350 

Kitchen 10300 

Hall 7035 

Second Floor. 

W. chamber 10050 

Alcove 7560 

S. chamber 7035 

N. chamber 7455 

Bath 3150 

E. chamber 5250 

Halls 2730 






cfi 



•^^ o 



P H OQ 

"la 

boo o 

1-1 "^ 



Cj 



"Q r I e3 



10395 
7035 
8085 

10300 
7770 

11055 
8316 
7035 
8190 
3465 
5250 
3003 



39 
27 
30 
39 
29 

42 
31 
27 
31 
13 
20 
12 



CO 

fl w p 



33.5 

38 

30 

32 

24 

22 
13 
26 
24 
7 
14.7 
14.7 



I 



The method used in determining the British 
thermal units lost from the room, given in column 
6, is the same as those given in the paragraph 
headed "Rules for Determining Loss of Heat." 
Take, for example, the parlor. The wall surface is 




Fig. 14. 
SECOND FLOOR. 



(78) 



Notes on Heating and Ventilation '79 

216 square feet. Divide this by 4; the result, 54 
square feet, is the equivalent glass surface. Add 
the actual glass surface, 36 square feet, which 
makes a total equivalent glass surface of 90 square 
feet. Multiply this by i^ times the difference be- 
tween the outside and the inside temperature, which 
gives the heat lost, or 90X105=9,450 B. T. U. lost 
from the room per hour. The remainder of the re- 
sults shown in column 6 have been computed in the 
same way. 

In Table XII the second column gives the B. T. 
U's as determined in Table XI; the third column 
the B. T. U.'s corrected for exposure, 10 per cent 
being added to rooms having north and west ex- 
posures, as, in this case, the prevailing winds are 
from the west. Column 4 gives the radiating sur- 
face required to heat the rooms with a two-column 
cast iron radiator. Column 5 gives the radiating 
surface as determined by Rule 3. 

The quantities in column 4 are obtained in the 
following manner. The steam pressure to be car- 
ried in the radiator is 5 pounds. The corresponding 
temperature of steam is 227 degrees. The tem- 
perature of the room is 70 degrees. The difference 
in temperature between the room and the steam 
will be 157 degrees. In the last column of Table 
VII the heat lost for a two-column cast iron radi- 
ator is given as 1.7 B. T. U.'s per degree difference 
per hour. Then the total heat lost per square foot 



80 Notes on Heating and Ventilation 

per hour will be 157X1.7=267 B. T. U.'s, that is, 
each square foot of radiator surface will give to 
the room 267 heat units per hour. Dividing the 
heat lost from the room, as given in column 3, by 
267, will give the results shown in column 4. 

In column 5 the radiating surface has been de- 
termined by Rule 3, which is sometimes called the 
Volume Rule ; that is, the cubic contents of the 
rooms are divided by a certain factor, depending 
upon the location of the room. A careful com- 
parison of columns 4 and 5, together with an in- 
spection of the plans, wnll show the inconsistency 
of the volume rule. The volume rule can be used 
only where the room has an average amount of 
cubic contents, as compared with its wall surface. 
To get the best results it is better to employ the 
method that has been used in determining the re- 
sults in column 4. 



CHAPTER IV. 



DESIGN OF INDIRECT STEAM HEATING SYSTEM. 

It is seldom thai indirect radiators only are in- 
stalled. This is due chiefly to the increased cost of 
installation and operation of such a plant, as com- 
pared with a plant using both direct and indirect 
radiation. In a residence heated by indirect radi- 
ation alone, it will be necessary to introduce an 
excess of air over that required by ventilation. 
This materially increases the cost of . operation. 
In designing an indirect heating plant the loss of 
heat from the building is figured in the same way 
as w4th the direct system. In using indirect radi- 
ation alone it will be necessary to introduce enough 
air so that the heat left in the room wiU supply 
the loss from the walls and windows. In order to 
determine the amount of surface to be placed in 
the room, it is necessary to know the temperature 
to which the radiator will heat the air and the 
amount of heat given ofif by the indirect radiator 
under different conditions of operation. >.H 

The amount of heat that miay be obtained from 
a given indirect radiator will depend upon the tem- 
perature at which the air is taken in, the tempera- 



82 Notes on Heating and Ventilation 

ture of the radiator, and the 
Heat Lost from , . ^ . . 

Indirect Steam ^^^ic feet of air passing 

Radiators. through the radiator. The 

following table gives the re- 
lation between the above quantities, assuming the 
temperature of the air entering the radiator to be 
zero, the temperature of steam in the radiator 22^ 
degrees, the temperature corresponding to 5 pounds 
gauge pressure : 

In school buildings and in buildings where the 
flues are of ample size the amount of air passing per 
square foot of radiating surface may be assumed to 
be 200 cubic feet per hour. In residences and build- 
ings where the flues are usually small, the amount 
of air passing per square foot of surface per hour 
does not exceed 150 cubic feet. 

From the results of the tests on indirect radi- 
ators given, the following points may be noted : 

If the temperature of the air entering the radiator 
is constant, then the temperature of the air leaving 
the radiator will decrease as the amount of air 
passing through the radiator is increased. 

In order to determine the amount of heat trans- 
mitted by the radiator it is necessary to assume the 
number of cubic feet of air that will pass through 
the radiator per square foot of radiation. You will 
also note the difference between the standard or 
short pin radiator (Fig. 15) and the long pin radi- 
ator (Fig. 16). As shown in Table XIII, the tem- 




Fig. 15. Short Pin Indirect Radiator. 




Fig. 16. Long Pin Indirect Radiator. 



84 



Notes on Heating and Ventilation 



peratiire at which the air is heated by the long pin is 
less than the temperature to which the air is heated 
by the short pin with the same quantity of air pass- 
ing. This is undoubtedly due to the fact that the pins 



Table XIII— Keat Losses from Indirect Radiators 


be . 


^ fee 




. k 




a;, a; o rt . 








C - 




Q.C* - . 


m fl 


^ "^ 




o 






m o 

. '5 


S-i 




ad 
















«M 


n '55 . 






"'' «y "^ -^^ _a 


O . 


ai oQ rj 






^ "" 'be 
^^fc CO 




^*3S 


W m O 


• ^- O) ^ j_^ 


•1^ 


g OJ OJ 


a ?, oj 

M (X)._ 


r; . Soto's 




O -M -t-J 

H 


1-^ 






Stan- 


Stan- 


Stan- 




dard Long 


dard Long 


dard Long 




pin. pin. 


pin. pin. 


pin. pin. 


50 


.147 140 


.125 .15 


.80 .95 


75 


.143 137 


.17 .21 


1.17 1.27 


lUU 


.140 135 


.24 .26 


1.51 1.60 


125 


.138 132 


.295 .31 


1.85 1.90 


150 


.135 129 


.355 .36 


2.22 2.20 


175 


.132 126 


.41 .405 


2.57 . 2.47 


200 


.130 123 


.47 .45 


2.90 2.72 


225 


.127 120 


.53 .49 


3.25 3.00 


250 


.123 118 


.585 .53 


3.60 3.20 


275 


.121 115 


.645 .57 


3.90 3.40 


300 


.119 112 


.700 .61 


4.22 3.60 













are so long that the ends become cooled. On the 
other hand, the long pin type is a very desirable 
type to use when one wishes to pass large quanti- 
ties of air, as the radiator has ample air passage. 
This is primarily the work for which it is designed. 



Notes ox Heating and Ventilation 



tb 



The short pin gives better results for ordinary 
houses where small quantities of air pass through 
the radiator. 



Table XTV — Indirect Radiators- 


-Temperature of 






liOaving Air. 




1 




>^ii'^ 




> ^ ,-^ ^ ' 






OJ-^ CO 








Q 




^ -M . 




.— i -'-' 




<V 












t^ 




Si «M 




r: 'w 




"S c 




"^oS . 




•=^^0 . 




-t-J 




-2? :y 




ilut) cr 




«j-i cd 




^y CS(N M 




«M 53 tH W 




OlZl 




0.2 




c.- 




^'V 




"^ ^ 




TS 




opS 


. 


0) ^ O q; 




<D « o a> 




U4 




^ ^ a 




^'^ a 




-5 




5 o) >j 




5 o) >j 




25 




cj ^ .ti .ii 




O) 




Oi o <i^ 


0) O 0) 


abj 


D 


atjo-^ o 


a fcjo— ^ a 


QB 






a .2 > o ^ 


ID 




(D 


a> 


H 




H 


H 




Standa 


rd Long 


Standard Long 




pin. 


pin. 


pin. pin. 





130 


125 


135 128 


10 


134 


128 


139 132 


20 


131) 


132 


144 136 


30 
40 


144 


136 
141 


149 140 
153 144 


148 


50 


153 


144 


158 146 



Indirect radiators are placed in a chamber or 
box, usually situated in the basement of the build- 
ing, as close as possible to the vertical flue leading 
to the room which they are to 
heat. The air is admitted to Installation of 
the radiator by a duct or flue. Indirect Radiators, 
connected with the outside 

air. This duct should be supplied with a suitable 
damper and, if possible, be so arranged as to close 



^6 Notes on Heating and Ventilation 



V^'.'.'sV'.A-.V'.VVVk-.S^^V'A'^^^^^^^^'^^^^^^^^^^^^'^' 




Notes on Heating and Ventilation ^'^ 

automatically when the steam pressure is taken off 
the radiator. The cold air is usually admitted di- 
rectly beneath the radiator and the heated air on 
leaving the room is taken off at one side. 

The casing surrounding indirect radiators is 
usually built of galvanized iron or of matched 
board, lined with tin. If of galvanized iron it 
should be bolted together with stove bolts, so that 
the casing may be easily removed. A much better 
method, but one which is more expensive, is to en- 
close the radiator in a small brick chamber with 
cement floor. This chamber should be large enough 
so that the radiator is accessible for repairs. Some- 
times a duct is provided in the radiator casing so 
that cold air may be taken around the radiator and 
mixed with the heated air through a suitable dam- 
per, controlled from the room which is heated. 
This is a very common arrangement in school build- 
ings. Fig. lo shows a sketch of an arrangement of 
this kind. 

The pipes or ducts leading from an indirect radi- 
ator should be carried to the room as directly as 
possible. It is better to have a long cold air pipe 
and a short hot air pipe. A long horizontal hot air 
pipe should be avoided. Where the air from the 
indirect radiator is to be used primarily for ventila- 
tion it is best to place the hot air register near the 
ceiling. 

The indirect radiators are usually suspended in 



88 Notes ox Heating and \'entilation 

the radiator chamber on iron pipes supported by 
rods hanging from the ceiHng. There should be 
at least lo inches clear space between the radiator 
and the bottom and top of the casing. The casing 
of the radiator should fit the radiator as closely as 
possible, so that very little air is allowed to pass 
around the radiator without being heated. Indirect 
radiators should be placed at least 2 feet above the 
v/ater line of the boiler, if they are to be operated 
on a o^ravitv svstem of circulation, and should be 
so arranged that the condensed water* wall drain 
from them without trapping. The tappings of 
these radiators are the same as for double pipe 
direct steam radiators. (See p70.) The following 
table gives the general proportions for an indirect 
radiator svstem : 



Table 


XV— Size of Flues for 


Indirect 


Radiator. 


Heating 
surface, 
sq. ft. 


Area 
of cold 
air supply, 
sq. in. 


Area 

of hot 

air suppl 

sq. in. 


Size 
of brick 
y, flue for 
hot air. 


Size 

of 

register. 


20 . . . 
30 . . 
40 . .. 
50 . . . 


30 

4."> 

60 

'. . , 75 


40 

60 

so 

100 
120 
100 
200 
240 
280 


8x 8 
8x12 
8x12 
12x12 
12x12 
12x16 
12x20 
14x20 
16x20 


8x 8 
8x12 
10x12 
10x15 
12x15 
14x18 
16x20 
16x24 
20x24 


60 


00 


80 . . 
100 


120 

150 


120 . . 
140 . . 


180 

.... 210 



It is usual to assume that the air enters the radi- 
ator at zero degree of temperature, in which case 



Notes ox Heating and Ventilation 89 

it will leave the radiator at about 130 degrees, the 

steam pressure in the radi- 
ator being 5 pounds and the Heating Effect of an 
velocity through the radiator Indirect Radiator. 

being 200 cubic feet per 

hour per square foot of radiator. Under the above 
conditions an ordinary pin radiator will give off 470 
B. T. U.'s per square foot, or, say approximately, 
450 B. T. U.S. Under these conditions the air en- 
tering the room will be at a temperature of 130 
degrees, and if the temperature of the room is 70 
degrees this air will be capable of losing to the 
room 60 degrees, or in other words, there is 60 de- 
grees of temperature available in this air for heat- 
ing purposes, or of 450 B. T. U/s given out by the 
radiator 210 B. T. U/s are available for heating 
the room. 

SOME RULES FOR IISTDIRECT HEATING. 

Rule i. A. For ordinary rooms. Divide the 
zvorll surface by 4, add the glass surface, and multi- 
ply the snm by .6. The quotient zmll be the amount 
of indirect radiation necessary to heat th? room. 

B. For entrance halls. Diz'ide the exterior wall 
surface by 4, add the glass surface and multiply the 
sum by .75, the product will be the number of square 
feet of indirect radiation. 

Rule 2. Figure the heating surface the same 
as for direct heating. Add 40 per cent. 



90 Notes on Heating and Ventilation 

Rule 3. Divide the volume of the room by 40. 
The quotient is the square feet of indirect surface 
required to heat the rooms on the first floor. For 
second and third fioor rooms divide by 50, and in 
stores and large rooms divide by 60. 

Take the same house that was used in the prob- 
lem for direct heating. In this case all rooms are 
to be heated by indirect radiation. It is in actual 

practice an unusual arrange- 

Example of Indirect ment, but it is figured out in 
Heating. this way as an illustration 

merely. 

The heat loss in this house will, of course, be 
the same in both direct and indirect heating and 
is given in Table XII (p. yy) . Assume that the 
air enters the radiator at zero degrees and leaves 
at 130 degrees; that the steam in the radiator is at 
5 pounds pressure and that 200 cubic feet of air is 
passed through the radiator per square foot of sur- 
face. From the results determined in paragraph 
headed ''Heating Efifect of the Indirect Radiator" 
each square foot of radiation gives off approxi- 
mately 450 B. T. U.'s. If the temperature of the 
room is 70 degrees only 60 degrees of the heat 
given to the air is effective in heating the room. 
As the total amount of increase in temperature is 
130 degrees, only approximately 6o-f-i30, or 45 per 
cent, is available for heating. As each square foot 
of indirect radiation gives off 450 B. T. U's, 45 



Notes on Heating and Ventilation ^1 

per cent of 450, or 200 B. T. U's, will be available 
for heating the room. The heat loss as given in 
the table for the parlor is 10,395 B. T. U's. Divid- 
ing this by 200 gives 52, the number of square feet 
of radiation required for the room. 

Fifty-two square feet of radiation passing 240 
cubic feet of air per square foot will pass 12,480 
cubic feet of air per hour; 12,480 is 3.47 cubic feet 
per second. Allowing a velocity 
of 5 feet per second, the area of Size of Hot Air 
the hot air pipe is 3.47 -:- 5 ^ .69 Tij^e. 

square feet. This equals 99 
square inches, which is the proper area of the pipe. 
The size of the cold air pipe leading to the radi- 
ator is usually made three-quarters the size of the 
hot air pipe. Table XVI gives the results for the 
whole house computed in the same manner as given 
above. In the table the odd figures and decimals 
have been left off. 

In selecting the size of radiator for a room, it 
is necessary to select those that vary by 10 square 
feet or more, as indirect radiator sections are not 
made smaller than 10 square feet per section. In 
a house where the radiators would be less than three 
sections, it is necessary to put two or three rooms 
on the same radiator, as it is not desirable to make 
very small indirect stacks. There is always danger, 
however, in taking the heat for two separate rooms 
off the same radiator, that the heat will not dis- 



92 



Notes on Heating and Ventilation 



tribute equally between the two rooms. When sep- 
arate rooms are heated from the same radiator, care 
should be taken to see that pipes leading to the 
two rooms have about the same leno:th and as nearly 
as possible the same resistance. 

A much more common ar- 

Combination of Di- rangement of indirect radiators 

rect and Indirect, is to put in just enough indirect 

radiation to give the proper 
amount of air for ventilation and supply the addi- 



Table XVI — Results of Computation, 




Indirect System. 








QQ 

O 

72 ^ 


o 

^ *-lH 


<v 


'O 6 


•M 


o 


' • o 


eg 


-u 5 


"^ 3 


n 


p^ 


■-s^ 


^ ~ 


Sc 


> . 


bI 


H S 


<D C 


cc±: 


cd.— 


C3 ^ 


S P 


Q. 




9^ ci 


t. ^ 


9- — 


p ^ 


^— 


'"?. 


^ 


*-^ 


-^ 


l^ 


First Fluok — 












Parlor 10,395 


50 
35 


100 
70 


75 
53 


12x12 
8x12 


900 
700 


Sitting room. . . . 7,035 


Dinirs: room .... 8,085 


40 


80 


GO 


8x12 


720 


Kitchen 10,300 


50 


100 


75 


12x12 


1.000 


Hall, L>(] floor. ..15.800 


73 


145 


110 


12x12 


1.500 


Skco.nd Floor — 












W. chamber. 












alcove 10,370 


93 


ISO 


1 35 


12x20 


l.GOO 


So. chamber.... 7,035 


35 


70 


50 


8x12 


700 


X. chamber 8,190 


40 


80 


GO 


8x12 


750 


Bath 3.465 


17 


40 


30 


6x 8 


300 


E. chamber .... 5.250 


24 


50 


35 


6x 8 


500 



tional heat for the room with direct radiation. Each 
svstem is installed as though the two were separate, 




Fig. 18. Arrangement of Flue Radiator. 



94 Notes on Heating and Ventilation 

except that they take their steam from the same 
steam mains and return into the same return pipes. 
In this system the direct radiators can be installed 
on the one-pipe system, but the indirect should be 
installed on the two-pipe system as indirect radia- 
tion does not work w^ell on a one-pipe system. It 
is not necessary to put indirect radiation into all 
the rooms of a residence. They are put into the 
principal living; rooms, the hall and the large bed- 
rooms. Where the house is small it may be neces- 
sary to put indirect radiation only in the sitting 
room and in the hall. An example of this kind will 
be taken up under the head of ventilation. 

Where only a small quantity 

of air is needed for ventilation 

Flue Radiators. ^^^^ radiators may be used in 

place of indirect radiators. 
The damper in the outside wall regulates the 
amount of air passing into the room and in ex- 
tremely cold weather this may be entirely closed. 
Table YIII on page 65 shows the heat loss from this 
type of radiation and the amount of air that the 
flues will pass. In figuring this type of radiation 
figure the same as for direct radiation and add 
25%. Each 30 square feet of flue radiation will 
furnish ventilation sufficient for one person. . 



CHAPTER V. 

STEAM BOILERS AND STEAM PIPING. 

Boilers are divided into two general classes—^ 
fire tube or tubular, and water tube or tubulous 
boilers. The commonest form of boiler used for 
heating purposes in this country is what is known 
as the return flue fire tube boiler. 

These boilers are adapted • to 

1 . r J J Types. 

plants of over 30 and under 150 

horsepower and where the pres- 
sure does not exceed 100 pounds. For pressures 
above 100 pounds it is customary to use water 
tube boilers. There is one exception, that is the 
Scotch marine boiler, which is a fire tube boiler 
and which can be made to withstand pressures of 
200 pounds and over in large sizes, as in this boiler 
the fire does not come in contact with the out- 
side shell. 

For heating purposes there have been introduced 
a number of special forms of boiler, a great many 
of these forms being built of cast iron. Cast iron 
boilers are not operated at pressures exceeding 10 
pounds. 

Any of these forms of boilers may be used for 
heating and the selection of the proper form will 



96 Notes on Heating and \'entilation 

depend upon the conditions in each particular case. 
In selecting a boiler the following points should be 
taken into consideration : The boiler must be of 
sufficient strength to withstand the maximum pres- 
sure to be carried. This does not usually exceed 
ID pounds. It must have sufficient heating sur- 
face in proportion to the grate surface to be 
economical. The stack temperature in a low^ pres- 
sure boiler should not exceed 450 degrees ; in the 
best plants it does not exceed 300 degrees. The 
boiler must have sufficient liberating surface so that 
the steam form.ed in the w^ater may escape from 
the surface of the water, without carrying a large 
quantity of water with it. The boiler must have 
large circulating areas so that the w^ater may be 
circulated freely to the heating surfaces and the 
steam formed may pass aw^ay from the heating sur- 
faces without restriction. The steam that forms on 
the heating surfaces rises in bubbles and is liberated 
from the surface of the water. If the boiler has 
insufficient liberating surfaces or the circulating 
areas are contracted the steam cannot rise rapidly 
enough and bubbles of steam remain on the heated 
surfaces. These bubbles prevent the w^ater from 
reaching the heating surfaces and as steam is a 
poor conductor of heat this results in an overheat- 
ing of these surfaces. This trouble may be very 
serious, especially in the water tube type of boiler, 
and results in the burning out of the tubes. In 



Notes ox HEATI^XT axd \'extilation 97 

cast iron boilers the lack of proper liberating sur- 
faces and sufficient steam space often causes ex- 
cessive priming. The question of circulating area 
and liberating surface is of more importance in a 
low pressure boiler plant than in a high pressure 
plant, as steam at 5 pounds pressure has about 
six times the volume of steam, at 100 pounds pres- 
sure ; so that to have relatively the same circu- 
lating area and liberating stirface in a low pressure 
boiler, we shotild have live times as much as in a 
high pressure boiler. 

In boilers for heating purposes it is desirable 
that they should have sufficient steam space, and a 
large storage of water, particularly if the plant 
is to be continuously operated. In boilers having 
large water storage it is possible to maintain a 
steam pressure on the boiler all night under banked 
fires. AMiere boilers are to be operated only occa- 
sionally, it may be desirable to have a small quan- 
tity of water, as each tin:e the boiler is started it 
is necessary to heat all the water in the boiler be- 
fore steam is formed. The ordinary fire tube re- 
turn flue boiler, on account of its large water stor- 
age, liberal circulating areas and large liberating 
surface, is a desirable one for heating purposes. 

The heating surfaces in a boiler are those sur- 
faces which have water on one side and hot gases 
on the other. A boiler should be so proportioned 



98 Notes on Heating and Ventilation 

as to transmit as much of the heat generated by 

the fuel to the water as possible. 
Proportion of Experience has determined that 
Boilers. for best results in boilers of 50 

horsepower and over a square 
foot of heating surface should evaporate not more 
than three pounds of water per square foot of 
heating surface. For small houses, where heating 
boilers of but a few horsepower are used, it is not 
usual to allow^ a square foot of heating surface to 
evaporate more than 2 pounds of water and when 
a square foot of heating surface evaporates more 
than the amounts given above, the transmission of 
heat through the plate becomics so rapid that all 
the heat is not removed ; the result is an exces- 
sively high stack temperature and a corresponding 
loss of heat. Surfaces that have steam on one 
side and hot gases on the other are called super- 
heating surfaces. It is not advisable to have super- 
heating surfaces in a boiler. 

The proportion of grate surface to heating sur- 
face depends upon the kind of fuel and the in- 
tensity of the draft. In small boilers used for heat- 
ing purposes it is usual to allow one square foot 
of grate surface to every 20 to 30 square feet of 
heating surface. For boilers 50 horsepower and 
over it is usual to allow from 30 to 40 square feet 
of heating surface per square foot of grate sur- 
face and in very large boilers the ratio is 50 to 60 



Notes on Heating and Ventilation 99 

square feet of heating surface per square foot of 
grate. 

The rate of combustion for anthracite coal will 
vary from 5 to 7 pounds of coal per square foot of 
grate surface per hour with average draft. With 
bituminous coal under similar circumstances, 6 to 
8 pounds will be burned in the smaller boilers and 
from 12 to 15 pounds in the larger sizes. 

The air opening to be allowed in the grates de- 
pends upon the kind of coal, but usually does not 
exceed 50 per cent of the area of the grate. An- 
thracite and the better grades of bituminous coaj 
do not require as large opening as do the slack 
coals. 

The term boiler horsepower as applied to boilers 
has no definite value and varies with local cus- 
toms, and the opinion of the manufacturer. 

The rating of a boiler should 

be the amount of steam it can 

. , . Boiler Horsepower. 

evaporate with good economy 

and without producing wet 
steam. In purchasing a boiler specify the number 
of square feet of heating surface the boiler should 
contain. This is a better criterion of the work that 
the boiler will do than the horsepower rating. The 
American Society of Alechanical Engineers has 
adopted the follow^ing rating for the horsepower of 
a boiler : 



100 Notes on Heating and Ventilation 



Table 


XVII 


Cast Iron 


Boilers 


for 


Steam 


Heating. 






-lJ 


CM 


7J 


u 

P4 


u 






«f-l 


6" 


^ -M 




d be 






. 


m 


oA<M 


C3 .^ 


o a 




•t-i 


C 




C 


of^ 


•n-- 




ao 






'4^ • aJ 
S 5Q etf 




1- 


o 


O 




be 

a 


O Q,^ 


-M CM 
CM 




(U 


cd 


<D 


•I^H 


«w :^ cj 




t^ . u 


B 

esj 


OS 




Oj 

0) 


• tM 00 






)^ 


tf 


o 


ffi 


m 


05 


a? 


A. . 


750 


5.04 


00 


17.8 


140 


.42 


B. . 


7U0 


4.8 


. . . 


• • • 


146 


« • • 


B. . 


800 


5.25 


• • • 


^ ^ 


155 


, 


C. . 


750 


6.25 


120 


19.2 


120 


6.25 


C. 


. 3,400 


25.00 


540 


21.6 


136 


6.3 



A boiler horsepon'cr is 34^/2 pounds of water 
evaporated from feed neater at 212 degrees, to 
steam at 212 degrees, zvhich is called the from and 
at evaporation. According to this rule, if three 
pounds of zvater are evaporated per square foot 
of heating surface, zve woidd allow from 10 to 12 
square feet of heating surface for each boiler 
horse pozver. 

In order to give some idea of the proportions 
used by the various cast iron boiler manufacturers, 
table XV^II has been compiled which embodies 

the practice of three makers of 

Proportions of standard cast iron heating boil- 
Boiler, ^^s. The different makers have 
been designated by the letters 
"A," "B," "C." . : 



Notes ox Heating and \^entilation 101 

STEAM PIPING. 

In designing a system of steam piping the three 
following considerations are the most important : 
First, that the piping shall be so arranged that all 
condensed water shall drain from it ; second, that 
it shall be free to expand, that is, so arranged that 
the joints shall not be strained W'hen the piping is 
heated ; third, that all points in the piping at which 
air would accumulate shall be provided with some 
means of removing the air. 

In this article the different parts of the piping 
system referred to will have the following mean- 
ing: 

Mains. — Mains are those pipes which lead from 
the boiler or boiler header to the submains or 
risers. Usually there are no radiators tapped from 
these mains. 

Risers. — Risers start from the mains in the base- 
ment or attic, and extend up or down through the 
building. From the risers the connections to the 
individual radiators are taken. 

Returxs. — All piping carrying condensed water 
from the steam mains to the boiler is included in 
the return svstem. The terms return riser, return 
main, etc., have the same significance as in the 
steam system. 

Reliefs or Drips. — A small pipe connecting the 
steam to the return system so as to carry condensed 



102 Notes on Heating and Ventilation 

water to the returns is called a relief or drip. Drips 
are used at all points where water would collect 
in the steam system. These drips are sometimes 
made of large pipe and called equalizing pipes, 
serving to equalize the pressure between steam and 
return mains in gravity return systems. 

Pitch. — The pitch of a pipe refers to its in- 
clination from the horizontal pipe lines. It is best 
that pipes should pitch with the current of the 
steam, so that the steam wall assist in the removal 
of the condensation. Return pipes are usually 
pitched toward the boiler so that the system may 
be drained at that point. 

Water Line. — The water line is the height at 
which the w^ater stands in the return pipes. In a 
well designed gravity system it is seldom more 
than six inches above the w^ater line of the boiler. 

Siphon. — When a vertical bend is made in the 
return main so that the return dips down and re- 
turns to its former level, it is called a siphon. All 
siphons should be provided with a drain (or pet 
cock). 

Dams. — Sometimes the water level in the boiler 
is lower than that desired in the piping system and 
an inverted siphon is placed in the return pipe. No 
return will then take place until the water has 
reached the highest point of this bend in the re- 
turn. A dam should be provided with an air cock. 

Water Seal. — Where a return pipe enters the 



Notes on Heating and Ventilation 



103 



return main below the water line it is said to be 
sealed. It is customary to seal all main riser drips 
and returns from indirect radiators and pipe coils. 




Fig. 19. 



Water Hammer. — The rattline and the ham- 



Jr» 



mering often heard in pipes is called water ham- 
mer. It is caused by steam coming in contact with 
water or surface in the pipes which is colder than 
itself. A sudden condensation results and a vacuum 



104 Notes on Heating and Ventilation 

is produced into which the water rushes. The 
blow is often so severe as to crack the fittings and 
spring the valves. It is most apt to occur when 
the plant is first started. Accidents from this cause 
may be avoided by admitting the steam very slowly 
at first. 

Steam Traps. — Steam traps are vessels usually 
placed between the steam and the return system to 
allow the water of condensation to be carried to 
the return system without steam entering the re- 
turns. By the use of steam traps the steam and 
return mains may have a wide difference of pres- 
sure. Steam traps are objectionable as they are 
liable to get out of order and require frequent re- 
pairs. 

The systems of piping may be grouped under 
three general heads. First, the one-pipe system. 
In this system the pipe carrying the steam to 

the radiator also returns the con- 
densed water from the radiator 
Systems of Piping. , ,, , ., o i . 

to the boiler. Second, two-pipe 

system, in which one set of pipes 
is used to carry the steam to the radiator and an 
entirely separate set of pipes is used to carry the 
return water to the boiler. Third, a combination of 
these two systems. The usual arrangement in the 
combination system is to run the mains on a two- 
pipe system, but the connection between the mains 
and the radiators is on the single pipe system. The 



Notes ox Heating and \'entilation 



105 



one-pipe system has certain fundamental advan- 
tages over the two-pipe system. In the one-pipe 
system the steam and condensed water are ahvays 
at the same temperature and as a resuk there is 




Fig. 20. 



very httle opportunity for water hammer. In the 
two-pipe system the steam and water being sep- 
arate the water may become considerably cooled be- 
low the temperature of the steam, and if at any 



106 



Notes on Heating and Ventilation 



point in the system it again comes in contact with 
the water we have condensation of the steam, 
vacuum forms, causing water hammer. In large 
plants, however, the one-pipe system is not desir- 




Flg. 21. 



able as it necessitates carrying a very large quan- 
tity of w^ater in the steam mains. 

One-Pipe System. — The simplest of all piping 
systems used in steam heating is what is known 



Notes on Heating and Ventilation 107 

as the one-pipe gravity system. In this system, 
the steam generated in the boiler flows through the 
pipes to the radiators where it is condensed. The 




Fig. 22. 

condensed steam in the radiators flows back 
through the same piping system to the boiler. This 
arrangement necessitates the condensed steam 
flowing back against the current of the steam. This 



108 Notes on Heating and Ventilation 

is objectionable as there is a tendency to trap the 
water. Because of this tendency it is good prac- 
tice to make the pipes larger in size than would be 
the case if the steam and water flowed in the same 
direction. In the one-pipe gravity system the pipe 
should always be given a good pitch toward the 
boiler. Figure 19 shows in diagram the piping and 
radiator connections for a one-pipe system. 

Two-Pipe System. — In the two-pipe system one 
system of pipes supplies the steam and another 
svstem carries off the water of condensation. The 
principal object in the two-pipe system is to avoid 
the accumulation of any great amount of water in 
the radiators or mains and in that way give a more 
positive circulation. Figure 20 shows the general 
arrangement used in the two-pipe system. The 
indirect radiators and pipe coils should always be 
connected on the two pipe system. 

Combination System. — In ordinary buildings 
the most satisfactory method is to use a combina- 
tion of the one-pipe and the two-pipe systems. In 
this system, as shown in diagram in Figure 21, the 
radiators and risers are on the one-pipe system, 
while the mains are installed on the two-pipe sys- 
tem. The svstem has this advantao:e over the one- 
pipe system of mains, that the mains are not 
obliged to carry so much water of condensation and 
can be freed from water from time to time. The 
one-pipe radiator connections of this system are 



Notes on Heating and Ventilation 109 

more desirable than the two-pipe radiator connec- 
tions in that there is but one valve to get into 
trouble instead of two and the steam and the water 
of condensation are always in contact with each 




Fig. 23. 

* other — thus avoiding the danger of water hammer. 
The risers may be one-pipe, as it is very seldom 
that we have difficulty with the circulation in using 
vertical risers. In most cases the one-pipe radiator 
connections and two-pipe mains will be found to 
give the best satisfaction. 



110 Notes on Heating and Ventilation 

OvERHE^AD Distribution. — In office buildings 
and buildings where the basement space is vaUiable 
for rental purposes, it is desirable to place the 
steam mains where they will occupy the least de- 
sirable space. It is customary to run a vertical 
steam main to the attic. A set of distributing 
mains is run through the attic, from which ver- 
tical risers extend down through the building with 
drip pipes connecting to the return system at their 
lower ends. The radiators are connected to the 
risers by means of single-pipe radiator connec- 
tions. This system gives very satisfactory results 
as in all cases the currents of steam and water are 
in the same .direction. In buildings exceeding four 
stories in height it is usually necessary to provide 
some form of flexible connection to allow for ex- 
pansion. A system of this kind is shown in Figure 

22, 

Gravity System. — Figures 19-22, inclusive are 
all shown for gravity return system and this sys- 
tem is the one commonly used for all small build- 
ings and for residences. In this system the steam 
and return mains are connected to the boiler with- 
out the introduction of pumps or traps, so that the 
condensed steam flows back to the boiler by gravity. 
Figure 23 gives a diagrammatic sketch of such 
a system. If the pressure at the surface of the 
water in the boiler is the same as the pressure of 
the surface of the water in the return mains, then 



Notes on Heating and Ventilation m 

the water level in the return mains and in the boiler 
will be the same. But if, as shown in Figure 2^ 
by the dotted lines, the pressure in the boiler is 5 
pounds and the pressure is only 4 pounds when it 
gets to the ends of the system, then the system is 
no longer balanced. It is necessary for the water 
to rise in the return mains until the column of 
water in the return mains is equal in height to the 
pressure of i pound, or approximately, it must 
rise about 2.31 feet so that the water in the re- 
turn main will be 2.31 feet higher than the water in 
the boiler, and this will be true for each i pound 
difference in pressure between the steam at the 
boiler and the steam at the extremities of the sys- 
tem. It is necessary, then, to be very careful to 
have ample sized piping in this system so that the 
pressure at all points of the return main will be 
about equal. In addition, it is necessary that the 
steam radiators, both direct and indirect, be at 
least 2 feet above the w^ater line. For the reasons 
given above it is not desirable to operate large 
plants on the gravity return system, as this system 
requires larger expense for steam mains and more 
or less difficulty will always be experienced in 
starting up the system. The systems of circulation 
involving traps and pump circulation will be taken 
up under the head of Central Heating Systems. 

There are a great many rules given for deter- 
mining the size of steam return mains, all of which 



112 Notes on Heating and \'entilation 

must be more or less modified to meet the partic- 
ular case in hand. In fact a very 
Size of Steam careful determination of the size 
Return Mains, of main is not necessary, as, no 

matter how carefully we calcu- 
late the size of the main, it is necessary to take the 
nearest pipe size. In determining the size of the 
main two conditions must be considered. First, 
it must be of sufficient capacity to allow of free 
circulation. This is the principal consideration in 
smaller buildings. Second, the mains must not 
produce more than a certain drop of pressure. 
This point is of particular importance in the de- 
sign of central heating systems. In the case of 
residences, the size is determined bv rules deter- 
mined by practice. In the second place, the laws 
governing the amount of pressure in steam pipes 
are fairly well known. They will be treated under 
the head of Central Heating Systems. The most 
rational method of finding the size of mains is by 
determining the velocity of steam passing in the 
main. Knowing the weight of steam passing in the 
main and having the pressure, the volume of steam 
passed through the main is known. This volume 
divided by the allowable velocity in feet gives the 
area of the pipe in square feet. The velocities al- 
lowed in various forms of mains are as follows : 

In steam engine connections from 75 to 100 feet 
per second. 



Notes on Heating and Ventilation H^ 

In exhaust steam mains from 75 to 150 feet per 
second. 

For steam heating work on the one-pipe sys- 
tem, 2 inches and under 10 feet per second. 

For two-pipe work pipes 2 inches and under 15 
feet per second. 

For two-pipe work pipes 2 to 4 inches 25 feet 
per second. 

For single-pipe work low-pressure pipes 2 to 4 
inches 15 feet per second. 

For single-pipe work low pressure pipes 4 inches 
and over 30 feet per second. 

Example. — Assume that a main is to supply 
2,000 feet of radiation. This radiation gives off 
approximately 1.70 B. T. U's per square foot of 
radiating surface per degree dift'erence of temper- 
ature. Let the temperature of the steam be 220°, 
the temperature of the room 70°. Then the total 
B. T. U's transmitted per hour will be 220 — 70 X 
1.70X2,000=^510,000. At 220° the latent heat of 
steam taken from the steam tables equals 966 B. T. 
U's. Then the steam used per hour will be 510,000 
-^-966=527 pounds of steam. At 220° each pound 
of steam has a volume of 22.95 cubic feet. Hence 
we have 527X22.95=12,000 cubic feet per hour 
or 3.3 cubic feet per second. For a velocity of 25 
feet per second we must have a pipe with an area 
of .134 square feet or 19 square inches. This is 
approximately the area of a 5-inch pipe. 



114 Notes on Heating and Ventilation 

Rule I. — The following is a very common rule 
for gravity return systems : To determine the di- 
ameter of the main leading from the boiler, point 

ofif two places in the number ex- 
Miscellaneous Rules pressing the radiating surface 

^ . and take the square root of the 

Steam Main. ^ 

remainder. To apply the above 
rule for indirect surfaces, multiply the indirect sur- 
face by seven-fifths arid proceed as for direct sur- 
face. As an example, suppose we are to supply 
2,000 square feet of direct radiation. We point off 
two places, which gives us 20. The square root 



Table XVIII— Pipe Sizes. 



"= -I 
o- o c "^ . 

</) _ oi C P 

Z o E (/)a 

5u 1 y2 

1 ou 2 

150 2 

2U() 2 V2 

230 2^2 

300 3 

400 31/2 

500 31/2 

600 31/2 

800 4 

1,000 41/2 

1,500 41/2 

2,000 5 

3.000 6 

4,000 7 

6,000 8 





% 




c 











= F 




iE 




iE 






n3 a> 




> <i^ 




> a» 






-^.v^ 




OC ^ 




a i^ 






>t 




>i 




>> 






E ^ 




E «« 




E "^ 






53 0) 




53 i; 




CO aj 










5; a 










'J) 0. 




c/3 a 




Kn a 




nch 


iy4 


inch 


IVa 


inch 


iy4 


inch 


nch 


iy2 


inch 


IV2 


inch 


iy2 


inch 


nch 


ly^ 


inch 


2 


inch 


ly? 


inch 


nch 


9 


inch 


2y2 


inch 


2 


inch 


nch 


2 


inch 


2y2 


inch 


2 


inch 


nch 


2V2 


inch 


3 ] 


nch 


2y2 


inch 


nch 


3 


inch 


3 


inch 


2% 


inch 


nch 


3 


inch 


3 


inch 


3 


inch 


inch 


3i/> 


inch 










inch 


3y2 


inch 










inch 


4 


inch 










inch 


4 


inch 










inch 


4 Mi 


inch 










inch 


5 


inch 










nch 


6 


incli 










inch 


7 


inch 











Notes on Heating and Ventilation ^^ 

of 20 is 4.48, which would make the size of the 
main 4^ inches. 

Table XVIII gives the common practice in pipe 
sizes : 

'The steam supply of the radiator should never 
be less than i inch. Steam mains in one-pipe work 
should not be less than 1^4 inches and in two-pipe 
work less than i^4 inches. The return connections 
to radiators should not be less than ^-inch and 
return mains should not be less than i inch. The 
drip pipe should not be less than ^-inch. Long 
horizontal pipes should be one-pipe size larger than 
the verticals in the same line. In the overhead sys- 
tem, especially where the building is over seven or 
eight stories, it is well to make the risers fairly 
large at the lower end to take care of the con- 
densed steam. These risers, even at the lower end, 
should not be less than 2 inches in size. 

Return Mains. — Return mains cannot be fig- 
ured for returning the water of condensation at a 
low velocity alone, but allowance must be made 
for the very sudden demands which occur when the 
plant is started and for the air carried with the 
water. The size of the return main is determined 
almost entirely by practical considerations. 

Table XIX gives the relative size of steam and 
return main and diameter of steam main. 

Return mains may be placed on a dead level, 
but as a rule it is desirable to give them some slight 



116 Notes on Heating and Ventilation 

pitch, to some point, preferably the boiler. At its 
lowest point there will be provided some sort of 
drain cock so that all condensed steam may be 
drained out of the system. The radiators, as well 



Table XIX — Relative 


Size of Mains. 


Diameter 
Steam Pipe. 


Diameter 
Return Pipe. 


11/2 
2 

^ /2 

3 
4 
5 
6 

12 


1 
1 
1^ • 

2V2 
3 
4 
5 

5 or 6 



as the pipes, should be set so that the condensed 
steam mav drain from them easily. It is alwavs 

3est to drain the condensed 

steam with the steam, in 

Pipe Drainage. which case the steam tends to 

free the pipes of the water 
of condensation. If mains are long, it is 
well to drain them at intervals to avoid carrying 
too much water of condensation with the steam. 
In the gravity return system where the drip pipes 
connect to the return system, there should be at 
least two fe^t difference in l^vel between the steam 
main and the boiler water level, in order to avoid 
the possibility of the water from the boiler being 



Notes on Heating and Ventilation H'^ 



forced back into the steam main. Check valves wiii 
not prevent it, the water of condensation will ac- 
cumulate in the steam main above the check. If 
it is necessary to drip the steam main at a point 
below or close to the water line, then it 
should be drained to a separate system of 
piping and the condensed steam accumu- 
lating in this piping should be forced back 
to the boiler bv some mechanical means. 




Fig. 24. 



Steam connections to steam mains should 
always be taken from the top of the mains 
so as to avoid the draining of the water of 
condensation into the connections. In over- 
head' systems of piping the steam mains may be 
drained directly through the risers as the amount 
of condensation is small compared to the number 
of drain pipes. In this case the risers may be taken 
from the bottom of the main. In connecting radi- 



118 Notes on Heating and Ventilation 

ators to the pipe system they should be set so as to 
have a sHght pitch in the direction in which they 
are intended to drain. Radiators set so that they 
cannot be entirely drained are a very common source 
of water hammer. 

The expansion of pipes in mains exceeding 50 
feet in length becomes an important consideration. 
It is customary to assume that in low-pressure 

steam piping there will be an 
expansion oi lyi inches per 100 
feet of pipe. In steam mains car- 
rying a pressure of 80 pounds 
or over it is customary to allow for an expansion 
of about lYz inches per 100 feet of length. There 



Expansion of Pipes. 




Fig. 25. 



are three general methods of taking up expansion. 

First, a simple means is by making offsets and 

turns in the pipe every 50 to 100 feet, the expansion 



Notes on Heating and Ventilation 119 



being taken iip by the spring in the pipe. This is 
shown in Fig. 24. This method is seldom used 
except in pipes under 4 inches. Another method 
and the method which it is most desirable to use, 
is to take up the expansion at all 90° turns. In this 
method the pipe w^hen it reaches the corner turns 
either up or down and the expansion is taken up 



//yj/////////////7777777. 





^/W/////////////>//. 



Fig. 26. 

by the movement around the vertical nipple in the 
elbows or tees at the corner. This method of taking 
up expansion is shown in Fig. 25. The author has 
had the opportunity of observing a system installed, 
in which expansion amounting to as high as 4 or 
5 inches has been taken up in swing joints and 
the joints (which have been in use for over seven 
years) have given no trouble whatever. 

The third method is by use of expansion joints. 
The use of expansion joints is in general not to be 
recommended. Fig 26 shows a cross-section of an 
expansion joint. Expansion joints are quite ex- 



120 Notes on Heating and Ventilation 

pensive and are always liable to leak and require 
attention. By carefully laying out the piping most 
systems can be installed without the use of expan- 
sion joints. The most serious difficulty occurs in 
the modern high office building. In buildings of 
not over ten stories expansion joints may be avoided 
bv anchorino: the risers in the middle so that thev 
expand in both directions, and allowing for a flex- 
ible connection between the risers and supply main 
in the attic and return main in the basem.ent. In 
this case the radiators in the upper and lower 
stories of the building must have allowance made in 
the radiator connections for expansion of the main. 

Another method that has been used to allow for 
expansion is by offsetting the pipe at about the mid- 
dle story. As, for exairiple, in a building of say 
i6 stories, run the riser up to the eighth story, then 
offset just under the ceiling of the eighth story for 
a considerable distance, usually not less than 20 
feet, and continuing the riser up at another loca- 
tion. The principal objection to this method is its 
appearance. In some cases it is difficult to avoid the 
use of expansion joints. In using expansion joints, * 
the joint should be anchored so that the expansion 
will go in a definite direction. 

A great deal of consideration should be given to 
the valving of a steam heating system. Gate valves 
should be used on horizontal steam mains, as they 
do not form a water pocket. If globe valves are 



Notes on Heating and Ventilation 121 

used on steam mains, they should Valves, 

be placed horizontally, that is, in 
a vertical pipe to avoid forming a steam pocket. 
Where it is possible to use it, an angle valve makes 
a very desirable form of valve. In large buildings 
where the plant will be under the control of an en- 
gineer, it is desirable to place valves on the steam 
risers and valves on the corresponding return risers. 
In residences it is w^ell to avoid valves, particularly 
on return mains. A valve on the return main is 
particularly dangerous as it may be closed by ac- 
cident while the system is in operation, in which 
case the radiator wall be filled with water and no 
water will be allowed to return to the boiler. 

Location of Mains and Risers. — Mains and 
risers should be located in as inconspicuous a place 
as possible, at the same time they should be acces- 
sible. The concealing of mains and risers in the 
building construction is ahvays a questionable prac- 
tice. If it is necessary to conceal the pipe it should 
be concealed under panels screwed on so that they 
can be removed in case of leakage or other neces- 
sary repairs. It is not wise to attempt to save in 
risers by making long radiator connections. The 
system will give much better operation by having 
frequent risers w^ith shorter radiator connections. 
Where risers are concealed in a building of wooden 
construction they should be carefully protected 
from the woodwork. 



CHAPTER VI. 



CONNECTIONS TO MAINS AND TO RISERS. 

In making the connections from mains to risers 
in a steam system there are three things to be con- 
sidered — the drip, the expansion, and free circu- 
lation. The simplest form of connection is shown 
in Fig. 27, and for general purposes it is perhaps 




Fig. 27. The simplest form of connection. Not desirable if ex- 
pansion at right angle is great. 

the best form of connection. The expansion of the 
main in the direction of its length is taken care of 
by turning in the threads of the vertical pipes. The 
expansion at right angles to the main, which is or- 



Notes on Heating and Ventilation 123 

dinarily very small, is taken care of by the spring 
of the pipes. If the expansion occurring at right 
angles were very large, then some other form of 
connection would be desirable. 

Fig. 28 shows a similar connection, but using ^ 
45-degree elbow in place of a 90-degree elbow at 
the main, as shown in Fig. 2y. This connection of- 
fers less resistance to the passage of steam than 
the connection shown in Fig. 2y ; on the 
other hand, it does not allow of as much 
expansion. The pipe rising from the main 




Fig. 28. Using a 45° ell instead of a 90°, as shown in Fig. 1. 

being at 45 degrees, there is a limited opportunity 
for any turning in the threads of the pipe and ex- 
pansion is taken up by the spring of the pipe. In 
this figure a drip is shown at the bottom of the 
riser. A drip is often placed at this point, particu- 



124 Notes on Heating and Ventilation 

larly in large buildings. In smaller plants con- 
densation is carried back through the steam con- 
nection itself, as in Fig. 27. In larger buildings it 
is undesirable to carry so much condensation 
through the horizontal pipes and a drip' is placed at 
the bottom of the riser, as shown in Fig. 28. 

Fig. 29 shows a connection similar to that in 
Fig. 27. It allows free expansion of the main, the 
same as Fig. 2y. In Fig. 29 all the condensation 




Fig. 29. Allows free expansion of the main ; requires a drip 
at the point where riser starts. 

which has occurred in the main up to this connec- 
tion will drain into the connection and it is there- 
fore necessary to place a drip at the point where the 
riser starts. A connection of this kind is often 
used where it is desired to meter different riser con- 



Notes on Heating and Ventilation 125 

nections for different consumers, then the conden- 
sation for each riser or each set of risers can be col- 
lected and metered with very little possibility of its 
coming back into the main. This is, in some re- 
spects, an undesirable form of connection. If for 
any reason the water level rises in the return system 
above the horizontal pipe connection to the riser 
then the ri^er will be entirely sealed from the main 




.■^/■ser^ 



Afc///-? 



Fig. 30. Often used in limited headroom. Usually undesirable. 

and it will be impossible to get steam into the riser. 
The writer has experienced this difficulty in places 
where it was necessary to use this form of con- 
nection. This happens particularly in gravity re- 
turn svstems. 

Fig. 30 shows a form of connection often used 
where there is very limited head room. As a gen- 
eral rule this form of connection is a very unde- 



126 Notes on Heating and Ventilation 

sirable one. It allows almost no expansion, all ex- 
pansion in such a connection must be taken up in 
the spring of the pipes. In addition to this, if the 
main happens to carry a large amount of water of 
condensation, part of this condensation may flow 
into the horizontal pipe and impede the circulation 
in the horizontal. Under the same conditions if a 






;/'%:v/"5' 




,^v/v/> 



Fig. 31. A different way of carrying off the drip ; used where 
drip is taken off at end of main. 

connection such as is shown in Fig 2y or Fig. 28 
were used, no difficulty would be experienced. 

Fig. 31 shows another method of carrying off 
the drip. This arrangement is used where the drip 
is to be taken away at the end of the main. It is 
very often desirable at such points, particularly if 
the main is long, to remove the air from the pipe. 



Notes on Heating and Ventilation 



127 



The figure shoWvS an air valve placed at the end of the 
pipe. Locating an air valve at the end of a main 
near the point of the drip facilitates the rapidity of 




Fig. 32. Drips from two mains to a single drip pipe. Simple 

but undesirable. 

the circulation in the main. In a great many installa- 
tions all the air in the system is taken care of by 



128 Notes on PIeating and Ventilation 

means of the radiator air valves. Such an arrange- 
ment, particularly if the house be large, always 



is 



/¥a. 



va/// 



s'-\-\<;'-^\s'^»tx-v i. i'- ' 



^ 



■^l 

^sN , ''^0 
< 









T^S 



fe 



Fig. 33. A better arrangement of dripping two mains into 

one drip pipe. 



makes the system, slow in circulation. In the larger 
systems it is absolutely imperative that the steam 



Notes on Heating and Ventilation 



129 



mains be properly relieved of air. In addition to 
making the steam slow in circulation, it causes un- 
equal expansion of the piping. This trouble will 
be taken up in another chapter. 








Fig. 34. Connection from main to riser where liead room is 
very short and expansion great. 

Fig. 32 shows the connection of the drips from 
two mains to a single drip pipe. Such an arrange- 
ment, while simple, is undesirable, as the condensa- 



130 Notes on Heating and Ventilation 

tion from one main often interferes with the con- 
densation coming from the other main. This would 
give very Httle trouble if the connection were made 
above the water line. The objection, however, to 
making such connection above the water line is that 
if the two currents of condensation which meet at 
this point are not at the same temperature, ham- 
mering or a chattering noise results. If placed be- 
low the line there is an opportunity for the two 
streams of water to interfere with the circulation. 

A better arrangement is that shown in Fig. 33, 
in which the two streams of water coming as drip 
from the steam mains would not strike ^ach other 
in the sam.e line ; the one stream, would How into the 
other. The union of the two streams should occur 
below the w^ater line of the system, if possible. 

Fig. 34 show^s a connection from main to riser, 

in which the head room is very short and it is de- 
sired to take up a large amount of expansion, the 

expansion being taken up by a swing on the short 

vertical nipple and by a swing on the riser. This 

connection has been used for tunnel mains where 

the head room in the tunnel did not permit of the 

other forms of connection shown. 

Fig. 35 show^s the connection between the main 
and the riser in an overhead system of distribution 
in which the rooms in the upper story are used 
and it is desired to conceal the piping connections. 

As shown in Fig. 35 it will be seen that the con- 



Notes on Heating and Ventilation 131 

nection from the main to the riser is carried in the 
space between the roof and the ceiling of the room 




Fig. 35. Connection from main to riser in overhead system of 

steam distribution. 

below. The connection from the main to the riser 
is taken from the bottom of the main. This is not 



182 Notes on Heating' and Ventilation 

objectionable in an overhead system, as each riser 
has a drip at the bottom and becomes in itself a 




Fig. 36. Horizontal connection long enough to care for some 
expansion of riser by the spring of the pipe. 

drip main, and in some cases this is the de- 
sirable thing to do, as it keeps the steam and 



Notes on Heating and Ventilation 133 

main entirely relieved of condensation at all points. 
In making connections between mains and risers 
an endeavor should be made to locate the main so 
that the horizontal pipe connecting main to the riser 
will be as short as possible. If it is necessary to 




Fig. 37. Simplest form ; short ; drains easily, but does not 
allow for expansion of riser. 



m.ake this a long pipe then the pipe should be made 
one pipe size larger than would otherwise be used 



134 Notes on Heating and Ventilation 

particularly in the single pipe system. In the double 
pipe system long horizontals are not so objection- 
able, as the riser may be dripped at its lower end, 
as shown in Fig. 28. 

In residence work it is usually found desirable 
to connect directly from the steam main to the 
radiators on the first floor instead of connecting 
these radiators to the risers. This direct connection 
from the radiator to the main insures a quicker cir- 
culation of the first floor radiators, which is usually 
found desirable in residence work. In building 
work this is not usually the case, the first floor radi- 
ators are connected to the main risers. 

The connection between the radiators and the 
risers should always be carefully considered. There 
are a great many forms of connection used between 

the radiator and the riser to 
Eadiator which it is connected. Each of 

Connections. these different forms of connec- 
tion has its advantage and dis- 
advantage, which must be considered in using any 
particular type of connection. Figures 36 to 42 
deal with single pipe work. 

Fig. 36 is the simplest form of connection. Its 
advantage is that it is short, simple and drains 
easily. The disadvantage of this form of connec- 
tion is that it does not allow of any expansion. 

The expansion of the riser would lift one end of 



Notes on Heating and Ventilation 135 

the radiator off the floor and in all probability pro- 
duce a leaky joint. 

Fig. 37 is a similar form of connection, but the 
connection between the valve and the riser is long 
enough so that a certain amount of expansion can 




Fig. 38. Desirable, clean, but floor must come up when the 

trouble-man comes. 

be taken care of by the spring of the pipe which 
connects the radiator valve and the riser. 

Fig. 38 is a very common form of connection used 
in residence work. The advantage of this connec- 
tion over the connections shown in Figs. 36 and 37 



136 Notes on Heating and V^entilation 

is that where the pipe passes over the floor there is 
always opportunity for dirt to collect around and 
under the pipe and it is difficult to sweep this dirt 
out. The connection shown places the horizontal 
pipe in the joist space. The long horizontal pipe 




Fig. 39. Similar to Fig. 3, witti position of radiator clianged. 

under the floor allows a certain amount of expansion 
due to the spring of the pipe. On the whole this is a 
desirable form of connection. Its principal objec- 
tion is that it cannot be easily reached in case of 
accident and it cuts the joists. The most common 
trouble with such connection is to have a sand 
hole in the elbow. Of course to repair this it would 
be necessary to take up the floor. 



Notes on Heating and Ventilation 137 

Fig. 39 is practically the same as Fig. 38, the po- 
sition of the radiator being changed. 




Fig. 40. Sometimes used on upper floors : horizontal pipe ex- 
posed below ceilings is an objection, ^yill do for store and 

undecorared rocms. 



Fig. 40 shows *the arrangement of radiator con- 
nection in which the horizontal is dropped down 



138 Notes on Heating and Ventilation 

under the ceiling of the room below. This con- 
nection is sometimes used on upper floors. The 
objection to it, however, is that the horizontal pipe 
coming just below the ceiling is very unsightly, 
and it should be used only where the horizontal 
pipe is exposed in store-rooms or through un- 
decorated rooms where such pipe would no' be 
objectionable. 




rig. 41. Used in office buildings ; good form for fireproof 

buildings. 



Fig. 41 is the plan of a connection very commonly 
used in office buildings. The connection is made 
from the riser to the radiator, passing the pipe be- 
yond the radiator and using a corner valve where 
the radiator connection attaches to the radiator. 
The principal objection to this arrangement is that 
it throv.\s the radiator out some distance into the 



Notes on Heating and Ventilation 139 




FiS. 42. Commonly used in residence work, where first floor 
radiators are fed from main in cellar. 



room and it is very difficult to sweep around the 
connection so as to keep it clean. In buildings of 
fireproof construction and where a large amount of 



140 Notes on Heating and Ventilation 

expansion is to be taken care of, this is probably 
the best form of connection to use. 

Fig. 42 shows a connection similar to Fig. 40 for 
first floor radiators. It is customary in most build- 
ings to connect the first floor radiator directly to 




Fig. 43. The simplest connection for a two-pipe system. 



the main and not to a riser. This arrangement is 
commxOnly used in residences. The connection is 
such that we have very easy turns and a very 
slight resistance for the passage of steam into the 



Notes on Heating and Ventilation 141 

radiator. It is particularly desirable where the 
system is operated at a low pressure. 

All the previous figures have dealt with single 
pipe connections. 

Fig. 43 show^s the simplest form of radiator con- 
nection for the two-pipe system. The objection to 
this arrangement is similar to the objection made 
to Fig. 36. That is, it is very rigid and will permit 
of almost no expansion and should only be used 
where the radiator is located at such a point that it 
is not necessary to take up expansion. The connec- 
tion is simple and direct, and from the standpoint 
of circulation, a desirable one. 

Fig. 44 shows a connection in which the expan- 
sion is taken up by means of the spring in the hori- 
zontal pipes. The verticals to the radiator valves may 
be made shorter and these connections can all be 
concealed in the joist space if desired. This ar- 
rangement can be used for buildings not more than 
three stories in height. Where buildings are higher 
the two-pipe connection should be made with a 
series of elbows, allowing for free expansion — 
something like that shown in Fig. 41. 

Fig. 45 shows a two-pipe radiator connection 
where the radiator is on the first floor and the 
horizontals are located in the basement. The same 
connection is shown with a horizontal pipe, allow- 
ing for expansion. In this case the return connec- 
tion is shown entering directly into the return main 



142 Notes on Heating and Ventilation 




Fig. 44. Expansion taken up by spring in horizontal pipes. 
lUsed in buildings not more than three stories in height. 

without any elbow. This is always undesirable, as 
the connection is very rigid, not allowing for ex- 
pansion, and should only be used where the con- 




Fig. 45. Radiator on ^-st floor and horizontals in basement. 

7} 



144 Notes on Heating and Ventilation 




Fig. 46. Connection for automatic system of heat control on 

the double-pipe system. 

nection will not be affected by expansion. If ex- 
pansion must be allowed for in the return main 



Notes on Heating and Ventilation 145 

then a connection similar to that shown for the 
steam main should be used. 

Fig. 46 shows the radiator connection for auto- 
matic system of heat control on the double-pipe 
system. In this case it is quite common to put the 
automatic on the steam supply and the check valve 
on the return. Then when the steam is turned off 
by the thermostat, the check valve automatically 
closes, and there is no possibility of the steam or 
water in the return main getting back into the radi- 
ator. If no check were placed upon the return a 
vacuum w^ould be formed in the radiator, due to the 
condensation, and the water would be drawn back 
from the return main into the radiator by this 
vacuum ; then when the steam was again turned 
on this water would cause a severe hammer in the 
radiator. 

In planning radiator connections for a building 
a long horizontal should be avoided, the length 
should be only sufficient to take up expansion. 

The location of the radiator should be carefully 
selected, so as not to occupy the best space in the 
room. For example, it is not uncommon to find 
the radiator in a bedroom occupying the only place 
in the room for the bed. The position of the radi- 
ators should be selected also with reference to the 
risers, so as to make the connections as short and 
direct as possible. The form of connection should 
be such as to allow for proper expansion. 



146 Notes on Heating and Ventilation 

Supporting of Pipes. — Horizontal pipes are usu- 
ally supported by the ordinary form of expansion 
hanger. As a rule pipes should be supported every 
ID feet and should be supported at points bearing 
the greatest weight. In placing a pipe support care 
should be taken to see that each support bears its 
proper proportion of weight. In buildings over 
three stories in height other methods should be 
taken to take the weight of the risers. An iron 
strap passing around the pipe and bolted to some 
portion of the building structure is usually the best 
means. Large piping is often supported by chains 
or on brackets with rollers. The supports of large 
pipes will be taken up under the subject of Cen- 
tral Heating. 



CHAPTER VIL 



DESIGN OF A HOT WATER HEATING SYSTEM. 

Hot water heating plants may be divided into 
two classes, those using natural circulation, and 
those using forced circulation. In residences and 
small buildings the system using natural circula- 
tion is almost universally used. It is simpler in 
construction and cheaper to install and operate. In 
central hot water heating systems and in the larger 
buildings the forced system of circulation is em- 
ployed. It is more certain in circulation, the size 
of the pipes may be smaller and in such buildings 
the system may be cared for by an expert attend- 
ant. The systems of forced circulation will be dis- 
cussed in connection with central heating. 

The arrangement of the 
hot water boiler and of the Natural System, 
piping in a hot water heating 

plant is similar to that of a two-pipe steam system, 
the difference is only in minor changes in the pip- 
ing system. The circulation in a natural hot water 
heating system is produced by the difference in 
the weight of the water in the cold and the hot leg 
of the system. It depends very largely upon the 
height of the water column in the cold leg. The 



148 Notes on Heating and Ventilation 

difference in the weight of the water in the two 
legs of the system is due to the fact that water 
Weighs less per cubic foot as its temperature is 
increased, namely : 

At 130° the weight of water per cubic foot is 
61.56 pounds. At 140° the weight of water per 
cubfc foot is 61.37 pounds. If, then, there were 
one cubic foot of water in both hot and cold legs 
of the system with a difference of 10° between the 
two sides, the force to produce circulation would 
be .19 pound. It will be seen from this that the 
force going to produce circulation is a small one 
and may be easily overcome by the resistance of the 
piping system. It is important, then, that in in- 
stalling a hot water system considerable attention 
be given to the arrangement of the piping. 

In designing a hot water 

Loss of Heat From system the losses of heat from 
Radiators. the building would be com- 

puted by the same rules as 
previously given for other systems. These losses of 
heat having been determined, it will be necessary to 
replace the loss by the heat given off by the radiator. 
In order to determine the amount of radiation nec- 
essary we must know what the losses of heat per 
square foot are for hot water radiators. Table 20 
gives the results obtained from hot water radiators 
tested under actual operating conditions with hot 
water. 



Notes on Heating and Ventilation 



149 



Table XX shows that the rate of transmission, 
as given in the last column of the table, is almost the 
same as for steam radiators. It will be safe 
to assume that the hot water radiator would 







• 
















TABLE XX. 






















k. 


»r u 




O 

■*•> 
eg 

♦a 




o 
c 


2 
o 

c 


i 

o 


a I- 


B.T U.pe 
er hour pe 
f. in temp. 




o 
•a 




a 


d 


a 


.£■::; 


= ■^•■5 




c 




53 


E 




5/i O- 


t/) ■ 01 




jvj 




H 


H 




-J 


qs"-^ 


38'' 


3-column cast 


iron. . 


. .187 


182 


72 


180 


1.67 


38" 


2-column cast 


iron. . 


. . .190 


185 


70 


200 


1.70 


38" 


flue radiator. 




. .182.5 


178.5 


70 


181 


1.65 



give off the same amount of heat per square 
foot whether filled with steam or hot water, the 
temperature inside and outside of the radiator be- 
ing the same. This, however, is not the case, as 
it is customary to operate a hot water plant at 
a temperature not exceeding i8o° or less. In 
calculating heating surfaces, the temperature of 
the water should never be assumed higher than 
i8o°. The temperature being about 220° under 
ordinary conditions in a steam radiator and only 
180° in the hot water radiator, the total transmis- 
sion in the hot water radiator is only about 75 per 



150 Notes on Heating and Ventilation 

cent of the transmission by the steam radiator 
using steam. 

There is another consideration in hot water heat- 
ing. The lower the temperature of the radiating 
surface the more uniform the temperature of the 
room and the more agreeable the heating effect. 
Where it is desired to heat almost uniformly all 
portions of a room, regardless of initial expense, 
it may be accomplished by installing very large 
heating surfaces. The reason for this is easily ex- 
plained. Where the radiating surfaces are kept at 
a high temperature, say 200° or over, at least 50 
per cent of the heat is given off by radiation and 
the remaining heat is given off by contact of air. 
When the temperature of the radiating surface is 
lowered a large proportion of heat is given off by 
contact of air and a smaller portion by radiation. 
This allows the air in the room to be at nearly 
the same temperature as the objects in the room. 
It is possible, then, in a hot water system to use 
quite different amounts of radiation, depending 
upon the effect desired. This may be illustrated 
by an example. 

Suppose a room to lose 10,000 B. T. U.'s per hour 
and that the heating surface has the same rate 
of transmission whether steam or water is used, 
and that this rate of transmission be 1.68 B. T. U. 
per square foot per degree difference of tempera- 
ture. In the first case, let the room be heated by 



Notes on Heating and Ventilation 1^1 

steam. The temperature of steam in the radiator 
be 220° and the temperature of the room 70°. Then 
the heat lost per square foot of surface would be 
(220 — 70) X the rate of transmission, 1.68=250 B. 
T. U. The number of feet of radiation required to 
heat the room will be 10,000-^-250 = 40 sq. feet. 

In the second case, suppose the room to be heated 
by hot water radiator at a temperature of 180°. 
Then the B. T. U. given off per square foot of sur- 
face w^ould be (180 — 70) X 1-68=185. The num- 
ber of square feet of radiation required to heat 
the room would be 10,000-^185 = 54 square feet. 

In the third case, assume a residence in which 
a very uniform heating condition is desired and 
the temperature- of the heating surface is not to 
exceed 150°. The loss per square foot of radia- 
tion would be (150 — 7o)Xi.68=:i35 B. T. U. 
The radiation required would then be 10,000^- 135 
= 75 square feet. The amount of radiation in hot 
water heating depends, then, upon the effect de- 
sired. 

In a closed tank system it would be entirely pos- 
sible to obtain a temperature as high as 240° or 
250°. In the open tank system the temperature 
should never exceed 180°, as a higher temperature 
than this would form steam in the tank and 
there would be danger of the water boiling, which 
causes a cracking, hammering sound in the piping 
system. 



152 Notes on Heating and Ventilation 

Rule I. — Divide the volume 
Rules for Hot Water of the room by 55. Add ^ 
Heating. of the exposed wall surface. 

Add the glass surface. Mul- 
tiply the sum of these by .4, the product will be the 
square foot of direct hot water radiation required. 
Rule 2. — For ordinary rooms divide the exterior 
wall surface by 4 ; add the glass surface and multi- 
ply the sum by .55. For entrance halls multiply 
the sum by .7. 

Rule 3. — Divide the volume of the room in cubic 
feet by the factors given below and the quotient 
will be the radiating surface in square feet. 

First floor rooms, i side exposed .40 

First floor rooms, 2 sides exposed 37 

First floor rooms, 3 sides exposed 34 

Second floor rooms 45 — 50 

Halls and bath rooms 35 

Offices 37—50 

In all these rules factors of exposure are to be 
allowed as given on page 2y, 

In order to understand better the methods of de- 
termining the heating surface required for a given 
house, take the same house as figured for steam on 
page 75. 

Take, for example, the parlor, assuming the out- 
side air to be at zero degrees and the inside air at 
70° The wall surface is 216 square feet and one- 
quarter of this is 54. Add the glass surface, 36 



Notes on Heating and Ventilation 1^3 

square feet, and multiply the sum by i^ times the 
difference between the temperature of the room and 
the outside air, or (54 + 36) X i>^ X 70 = 9,450 
B. T. U.'s. To this add 10 per cent for exposure, 
which gives the loss as 10,395 B. T. U/s per hour. 
In Table XXI the second column gives the B. 
T. U.'s, as determined in Table XII, column 3. Col- 
umn 3 gives the radiation in square feet for a two 
column radiator. Column 4 gives the radiation as 
determined by Rule 3, the volume rule, the vol- 



TABLE XXI. 

Results of Computations — Direct Hot Water. 

-:: t: « t: t:l5 

6 3 w 3 3-j^ 

2— <^ c c '^^ "^ ^ 

"■5 ' "^ "2 -^ 

OQ 

First floor — 

Parlor ". 10,395 68 45 68 

Sitting room 7,035 46 52.5 50 

Dining room 7,350 48 48 48 

*Kitchen 10,300 67.5 47 40 

Hall 7,035 46 32.5 48 

Second floor — 

W. chamber 10,050 65 39 65 

Alcove 7,560 49 18 40 

S. chamber 7,035 46 34.5 46 

N. chamber 7,455 49 32 50 

Bath 3,150 20 12 20 

E. chamber 5,250 34 25 34 

Halls 2,730 18 25 20 

♦Just enough radiation to keep from freezing in ex- 
tremely cold weather. 



154 Notes on Heating and Ventilation 

umes of the rooms being taken from Table XL 
Column 5 gives the radiation that would actually 
be used. The quantities in column 3 are obtained 
as follows : Assume the temperature of the water 
entering the radiator at 175° and that of the tem- 
perature of the water leaving the radiator 165°, 
then the average temperature in the radiator is 
160°. The temperature in the room is 70°, the 
difference being 90°. The rate of transmission as 
given in Table XX, line 2, is 1.70 B. T. U. The 
total transmission per square foot per hour is, then, 
1.70X90=153 B. T. U. Dividing the heat lost 
from the room, column 2, by 153, or the loss for 
each square foot of radiation, will give the results 
in column 3, the number of square feet of radia- 
tion required. In column 4 the radiating surface 
has been determined by the volume rule, Rule 3, 
and shows the inconsistency of this method of fig- 
uring though it is a method very commonly used. 
This method should never be used except as a 
check. When the volume rule shows very much 
larger results than the other rules it is well to add 
surface to the radiator to allow for the increase in 
volume. This has been done in column 5. In re- 
gard to proportioning of radiation one can never 
trust absolutely to his figures and should always 
carefully compare his results with the room and its 
exposure and use his judgment in regard to 
changes that seem desirable. 



CHAPTER VIII. 



HOT WATER BOILERS AND PIPING. 

Hot water boilers are practically the same as 
steam boilers. Any good form of steam boiler may 
be changed to a hot water 

boiler by filling the steam Hat Water Boilers, 
space with water and allowing 

the water to go in at the lowest point of the boiler 
and go out at the highest point of the boiler. In 
boilers especially designed for hot water heating 
no space is left over the tubes, the whole boiler shell 
being filled with tube surfaces. This makes the hot 
water boiler more compact for the same amount of 
heating capacity than the steam boiler. The circu- 
lation in the hot water boilers is probably slower 
than in steam boilers and there is much less local 
circulation. The cold water enters from the bot- 
tom, passes over the tubes and leaves at the top of 
the boiler. The heat transmitted per square foot 
of surface is practically the same in steam and hot 
water boilers. The proportions of heating surface 
to grate surface and of grate surface to chimney 
area may be taken the same for hot water as for 
steam. 

In large hot water systems the ordinary fire tube 
boiler is used. The principal modification of the 



156 Notes on Heating and Ventilation 

boiler would be to fill the steam space with tubes 
and make the return opening same size as the steam 
opening. For residence work cast iron, sectional 
boilers are usually used and these are suitable for 
all similar work, except wdiere high pressure is 
used. In high pressure hot water heating, cast iron 
boilers are not permissible as these boilers are not 
usually made to withstand pressures exceeding 20 
pounds. A pressure of 20 pounds corresponds to a 
water column 46 feet high and this is about the 
height of an ordinary four-story building. It is 
not desirable to use cast iron boilers in buildings 
more than three stories high, above that height 
wrought iron boilers should be used so as to with- 
stand the' static pressure due to the height of the 
water. Cast iron boilers would not oe suitable for 
hot water systems using a closed tank and having 
the water under pressure. Boilers for these 
systems are usually made to withstand safely a 
pressure of 100 pounds per square inch. The pro- 
portions of cast iron boilers for hot water heating 
are given in Table XXII. In this table the rating 
of the boiler does not include the piping. In select- 
ing the boiler the square feet of radiation equiva- 
lent to the piping must be added to the square feet 
of radiator surface. In the average house these 
boilers will carry .6 of their rating in actual radia- 
tion, exclusive of piping, provided the piping is 
covered with some good grade of pipe covering. 



Notes on Heating and Ventilation l^'^ 

Table XXII is based on approximately the fol- 
lowing, allowing one square foot of grate to each 
30 square feet of heating surface, and one square 
foot of grate to each 300 square feet of radiation. 
(This radiation must include the radiating surface 
in the mains.) 

In designing a hot water 
piping system the most im- Hot Water Piping. 
portant consideration is the 

resistance of the piping. The resistance of the 
piping should be almost the same for each radiator 
at the same level and the friction of the piping sys- 
tem should be kept as low as practicable. 

Definition of Terms Used. — The different 
parts of the piping system referred to will have the 
following meaning. 

Flow Mains and Flow Risers. — The flow 
mains and flow risers are those portions of the 
piping system which carry hot water from the boiler 
to the radiator. The word flozv always refers to 
the hot side of the system. 

Return Mains and Return Risers. — The 
terms return mains and return risers refer to pip- 
ing which returns the cold water from the radiator 
to the boiler. 

Expansion Tank. — The expansion tank is a 
vessel partly filled with water and partly filled with 
air which allows for the variation of the volume of 
water in the system with the changes of the tem- 



158 Notes on Heating and Ventilation 

perature of the water. In the open tank system 
this tank is situated at the highest point of the 
system. In the closed tank system it may be lo- 
cated anywhere in the building. 



TABLE XXII. 
Proportion of Cast Iron Hot Water Boilers. 



c 

O T3 


b4 


a> 






■*- C 




-*-> 


oj !2 


a 


.2 5 

T3 to 




0« <j 


•11 


3 


— p3 

VI- '-J- 


C7 


o <u 


o 

E 




C/3 


C/) 






(/] 








. 



300 25 1 2 8 

400 30 1.3 2 8 

500 40 1.6 2V2 9 

750 60 2.5 2V2 9 

1,000 80 3.3 3 9 

1500 120 5.0 SV2 10 

2.000 160 6.5 4 H 

2 500 200 8.5 5or2-3y2 12 

3 000 250 10.0 6 or 2-4 14 

S'SOO 280 11.5 6 or 2-4 16 

4 000 330 13.5 6 or 2-5 18 

5*000 400 16.5 7 or 2-5 26 

6000 500 20 8 or 2-6 22 

T^OOO 575 23 8 or 2-6 24 

8 000 650 26.5 2-7 or 3-5 26 

9000 750 30 2-7 or 3-5 26 

lO'oOO 800 33.5 2-8 or 2-6 28 

II'OOO 900 36.5 2-8 or 2-6 28 



Pitch. — The pitch of the pipe refers to its in- 
clination from the horizontal. 

Legs of the System. — The flow main is often 
termed the hot leg of the system and the return 
main the cold leg of the system. 



Notes on Heating and Ventilation 1^9 




Figure 47. 



160 Notes on Heating and Ventilation 

Four systems of piping are 
Systems of Piping, used — the multiple circuit 

system, the single circuit sys- 
tem, the overhead system, and the single pipe sys- 
tem. 

Multiple Circuit System. — This system is the 
one most used and is sometimes called the standard 
system of piping. This system is shown in Fig. 47. 
The flow main rises from the top of the boiler to 
a convenient height just below the basement ceil- 
ing so as to allow for pitch towards the boiler of 
not less than ^ an inch in 10 feet. This main or 
mains is carried around the basement so as to sup- 
ply the risers. Too many risers should not be 
taken from one set of mains, as the radiators at 
the end will be too much cooled. The main re- 
turn is parallel to the flow^ main and of the 
same size. The open expansion tank is placed 
at least 3 feet above the last radiator and 
should be connected to the nearest riser. The 
connection to the expansion tank should be at the 
bottom of the tank. In this system the branches 
from the flow main usually supply only one radiator 
on the first floor, a separate branch being run to 
the radiators on the second and third floors. At the 
points A and B, Fig. 47, where the riser branches to 
go to -the second floor, the risers ofifset. This is 
done to prevent too rapid circulation in the radiators 
above, the tendency being for the second floor ra- 



Notes on Heating and Ventilation 161 







Figure 48. 



162 Notes on Heating and Ventilation 

diators to take all the water and prevent circulation 
in the first floor radiators. This is a reason why it 
is preferable to connect first and second floor radi- 
ators separately to the flow main. The circulation 
in the hot w^ater system depends upon the vertical 
height of the system. The higher the main the more 
rapid the circulation. This makes it necessary to 
put additional turns in the risers going to the upper 
floors or add to the resistance in the piping system 
so as to make the resistance to each floor propor- 
tional to the efifective head producing circulation 
at that floor. 

Single Circuit System. — In the single circuit 
system, as shown in Fig. 48, the water flows di- 
rectly to the radiator from the boiler through a 
pipe to which no other radiator is connected and 
is returned to the boiler by a separate pipe. A large 
number of these circuits may be connected to one 
boiler, each one being entirely separate from the 
other. This is one of the earliest forms of piping 
systems used for hot water work. It gives good 
results but is expensive to install and makes an 
extremely complicated piping system. 

Overhead System. — The overhead system is 
shown in Fig. 49. In this system the flow main 
is carried directly from the boiler to the highest 
point in the system, usually the attic. From this 
flow main risers extend to the basement and con- 
nect to the main return. This svstem is sometimes 



Notes on Heating and Ventilation 1^3 




Figure 49, 




Figure 50. 



Notes on Heating and Ventilation 1^^ 

modified as shown in Fig. 50. In this case the 
riser in both flow and return main to the radiator 
takes its supply at a point near the level of the 
radiator and delivers the water at a point below 
the level of the radiator in the same main. One ob- 
jection to this arrangement is the fact that the 
radiators on the upper floor will be considerably 




Figrure 51 



warmer than the radiators on the lower floors, and 
where this system is installed larger radiators 
should be used on the lower floors. It has the 
advantage of simplicity. 

In the systems described, w^ith the exception of 
Fig. 50, the circulation from flow to return main 



166 Notes on Heating and Ventilation 

takes place through the ra- 
Open and Closed Circuits, diators. This is what is 

termed an open circuit. In 
the open circuit system, where two or three radi- 
ators are closed off, the resistance to circulation is 
greatly increased and the system will be slow to 
circulate when the radiators are opened. This may 
be avoided by connecting up the piping system as 
shown in Fig. 51. The closed circuit system is par- 
ticularly desirable in large buildings, especially 
buildings having very long horizontal mains. 

In this system the hot water main acts as both 
flow and return main, the radiators being con- 
nected on the two-pipe sys- 
Single Pipe System. tems as shown in Fig. 52. 

It is necessary in the single- 
pipe hot water system to make the mains very large 
in diameter, as the current in them must be rela- 
tively slow. In this system the hot water passes 

along the top of the main and the cold water passes 
along the bottom of the main. It is necessary, 

then, that the flow riser going to the radiator be 
connected to the top of the main and the return 
riser coming from the radiator be connected to the 
bottom of the main. The main itself is usually in- 
stalled on a closed circuit, as shown in Fig. 52. 
The single-pipe system of distribution has not been 
extensively used and has no great advantage over 
the standard system of piping. 



Notes on Heating and Ventilation 167 




Figure 52. 



As previously stated, the hot water system should 
be so designed that the resistance of flow to each 



168 Notes on Heating and Ventilation 

radiator should be pro- 
Velocity of Flow. portional to the force pro- 
ducing flow. The water 
will always seek the path of least resistance, so that 
the radiators having the smallest pipe resistance 
will receive the largest quantity of water, and radi- 
ators having the largest pipe resistance will be pro- 
portionally colder. A series of experiments 
have been made at the University of Michigan 
to determine the velocity of water in a hot 
water heating system under actual conditions 
of operation with full sized pipes and radiators. 







TABLE 


XXIII. 




Velocity- 


Of 


Hot Water 


Circulation 


(Feet per 






Second.) 




Height of 








circuit 


in 


— Difference in Temperature. — | 


feet. 




10. 


15. 


20. 


5 




.135 


.39 


.55 


10 




.19 


.56 


.78 


15 




.235 


.69 


.95 


20 




.27 


.79 


1.09 


25 




.30 


.88 


1.22 


30 




.31 


.96 


1.34 


40 




.38 


1.11 


1.53 


50 




.425 


2.25 


1.74 



The actual velocity was found to vary from one- 
quarter to one-half of the theoretical velocity, de- 
pending upon the difference in temperature be- 
tween the hot and cold leg of the system. In Table 
XXII I the actual velocities have been computed 



Notes on Heating and Ventilation 1^9 

from the results obtained by these experiments for 
different heights and different conditions of tem- 
perature. 

No complete set of experiments has been made 

to determine the resistance of pipe and fittings. 

The University of ]\Iichi- 

, ,, ' . . . Resistance of Pipe 

o'an at the present tmie is , ^.^^. 

^ . ^ , ^ and Fittings. 

making a series of experi- 
ments, but these have not yet been completed. The 
following are the ordinary assumptions that have 
been made : 





• 


TABLE XXIV 


, 






Size 


of 


Hot Water 


Mains. 




Diameter 


Total Leng'tli of Circuit in Feet 


. 


of mains. 


50. 




100. 


200. 


300. 


1 


40 




30 






ly^ 


60 




45 


30 


, , 


1V2 


90 




60 


40 


30 


2 


160 




120 


70 


60 


21/2 


250 




200 


120 


110 


. 3 


350 




300 


200 


190 


31/2 


500 




400 


330 


2a0 


4 


650 




500 


450 


350 


41/2 


900 




700 


650 


500 


5 


1,200 




1,000 


800 


650 


G 


1,500 




1,200 


1,200 


1,000 



Resistance of standard elbow=25 feet of pipe. 

Resistance of standard tee=25 feet of pipe. 

Resistance of standard return bend=35 feet of pipe. 

Resistance of the ordinarv radiator connection from 
the flow main through the radiator to the return 
main is equivalent to about 100 feet of pipe. 



170 Notes on Heating and Ventilation 

The size of pipe may be figured by assuming the 

actual velocity due to the head and calculating the 

size required to carry a 

Size of Pipe. given amount of water. 

This is usually done in 

large buildings. In smaller buildings it is customary 

to follow the rules used in good practice. 

Table XXIV gives the pipe sizes of the mains to 

supply different quantities of direct radiation at 

different distances from the boiler. In establishing 

the size of the risers it is customary to start with 
a riser the same size as the radiator connection and 

carry the riser down to the floor below where the 

next radiator connects. If the radiator does not 

exceed 60 feet in size, add one pipe size to the pipe. 

Table XXV gives the size of risers for various 
quantities of radiation on different stories. 

The following are the radiator tappings for hot 
water radiators : 

Radiators containing 40 sq. ft. and under. . .1 inch 
Radiators containing above 40 sq. ft. and not ex- 
ceeding y2 sq. ft 1 54 inch 

Radiators containing above 'J2 sq. ft \V2 inch 

Hot water piping should be pitched away from 
the boiler and arrangements should be made so that 
Air Valves, Pitch and Sup- the piping and boiler can 
port of Pipes. be drained. This is neces- 

sary on account of freezing if the plant is not kept 
in operation. The piping should be supported the 



Notes on Heating and Ventilation I'^'l 

same as for steam pipes, with supports about every 
lo feet. Care should be taken that the pipes are 
straight, as any sudden elevation in the pipe will 







TABLE XXV 








Si 


ze of 


Hot 


Water 


Risers. 




Diameter 














of Riser, 


He 


ight of Radiator above Boiler 


in Feet. — 


inclies. 


5. 


15. 




25. 


35. 


45. 


1 


30 


40 




50 


60 




11/4 


40 


60 




70 


80 


'96 


11/2 


90 


100 




120 


135 


150 


2 


160 


180 




220 


260 


300 


2V2 


250 


290 




350 


400 


500 


3 


360 


450 




550 


650 


750 


31/2 


500 


620 




750 


900 


1,000 


4 


700 


800 




1,000 


1,150 


1,500 



form a pocket in which air will collect, and this col- 
lecting of air in the pocket will prevent the flow of 
water. An accumulation of air in the pipe will stop 
the circulation almost as effectively as a valve. The 
expansion of pipes by heat must also be taken care 
of as in the steam system. All branches going 
from the piping system and supplying radiators be- 
low the level of the mains should come off the bot- 
tom of the fiiain, so as to prevent air accumulating 
and sealing the pipe. 

All radiators and high points in the mains where 
air will collect should be provided with air valves. 

There are special air valves made for hot water 
work. These will be described later. 



CHAPTER IX. 



VENTILATION. 



The necessity of ventilation, that is, of renewing 
the air in a closed room, is due, first to the vitiation 

of the air by the products 
Necessity of Ventilation, of respiration from the 

persons in the room ; sec- 
ond, to the products of combustion from artificial 
illumination ; third, to the heat generated by per- 
sons and lights in the room ; and, fourth, to the 
presence of gases from chemical processes. 

In a small house or a small school building ven- 
tilation is very easily produced by methods which 
employ natural draft, such as hot air furnaces, 
steam and indirect radiators. In all systems using 
natural draft, the force of the draft depends upon 
the difiference of the temperature between the air 
inside and that outside the flue. ' Where this differ- 
ence amounts to only 30° or 40° the difference in 
the weights of the columns of air is so small that 
the force producing draft is very light and may be 
easily overcome by external conditions. In larger 
buildings it is not possible to use natural draft as 
the flues become excessive in size and are not cer- 



Notes on Heating and Ventilation^ i'^S 

tain enough in their operation. This has led to the 
use in school buildings and other public buildings 
of a forced system of ventilation in which the cir- 
culation is produced by a fan or system of fans. 

The perfectness of the ventilation in a room is 
ordinarily determined by the amount of carbonic 
acid gas. Carbonic acid gas is not poisonous in 
itself. Its injurious effects are produced entirely 
by the reduction of the oxygen in the room. There 
are, however, other injurious gases given off from 
the body, together with the carbonic acid gas. 

The lungs take in oxygen from the air, which 
combines with the tissues of the body, forming the 
products of combustion 

which are given off by the Products of Respiration, 
excretory organs — lungs, 

skin, etc. The principal excretions removed 
by the lungs are carbonic acid gas, water 
vapor mixed with other gases and some ani- 
mal matter. These excretions, together with excre- 
tions from the skin, produce a disagreeable odor and 
may be poisonous. The average man when sitting- 
still consumes in breathing from 19 to 25 cubic 
feet of air per hour, and when exercising from 26 
to 35 cubic feet per hour. The amount of carbon 
dioxide and water vapor given off per hour by 
human beings is given in table XXVI. 

The products of combustion from the sources of 
heating, such as grates, stoves, etc., are drawn off 



174 Notes on Heating and Ventilation 





Table XXVI- 


-Air 


Pollution 


Tests. 




Subject to Test 




At Work 






At Rest 




• 




0^: 


V) 

O.E 

CM C3 






^3 


0.E 

•a 


Laborer . 


.45 


81 


1.515 


2.03 


69 


20 


.551 


1.12 


Laborer . 


.77 


47 


1.423 


8.05 


78 


26 


.586 


2.55 


Clerk . . . 


.64 


44 


1.331 


1.76^ 


I 69 


29 


1.141 


1.19 


Draughts- 


















man . . 


.69 


41 


1.61 


1.61 


^ ^ 


^ ^ 


• • • • 




Average 


















man . . 






* '.600 


.... 


66 


63 


.412 


1,365 


Woman . 


. 


Bov 


. . . 


^ ^ 


.48 


• • • • 


, ^ 


, ^ 


• • • • 




Girl 


. . . 




.39 


. . . . 






.... 





by the chimney, but the 
Products of Combustion, products of combustion 

from the hghts in a room 
pass directly into the room. Lights give off 
carbonic acid gas, watery vapor, and traces of sul- 
phuric acid. Table XXVII gives the consumption 
of combustibles and the generation of carbonic acid 



Table XXVII —Pollution of Lighting. 

Consumption of com- Carbonic acid 

bnstible per C. P. per C. P. in 

Source. in cu. ft. per hr. cu. ft. per hr. 

Gas— Fishtail burner 802 — .527 .494 — .304 

Gas — Argand burner — .445 .254 

Gas — Welsbach burner . . . .05.3 — .024 .030 — .057 

Petroleum, round burner. .Gals. .00050 .112 

Petroleum, small flat bnr. .Gals. .00198 .335 

Wax candles Oz. .271 .417 

Paraffine candle Oz. .324 .459 



Notes on Heating and Ventilation 1"^ 

gas by ordinary forms of lighting. The table is 
given for each normal candle power . 

The products of chemical operations should never 
accumulate in a room so that the odor is per- 
ceptible. In some industrial 

processes it is almost impos- Chemical Processes, 
sible to avoid a certain 

amount of concentration of the gases. In such a 
case the chemical products should be sufificiently 
diluted with fresh air so as not to produce injurious 
effects upon the occupants of the room. 

Table XXVIII gives the relative dilution re- 
quired for different gases in cubic feet per loo cubic 
feet of air . 

The amount of heat generated by a human be- 
ing varies with age, activity and temperature of 
the surrounding air. The 

average amount of heat Generation of Heat "by 
given off by an adult is Human Beings, 

about 400 B. T. U's per 

hour, and by a child about half that amount, or 
200 B. T. U's per hour. Of 400 B. T. U's 
given off by human beings about 30 per cent 
is lost by contact of air and about 43 per cent 
by radiation, the balance is lost by exhalation and 
other losses. Comparing this with the average 
steam radiator, we see that a child is equal to about 
eight-tenths of a square foot of radiation and an 
adult man is equal to about one and eight-tenths 



176 Notes on Heating and V'entilation 

of a square foot of radiation. This becomes a very 
important point in the heating of large lialls, par- 
ticularly if they are very crowded and have very 
little external wall space, as the heat given ofif by 



Table XXVIII-~Air Dilution. 



Detrimental effect occurs 
in several hrs. in i/^-l hv. 



Iodine vapors 00005 .0003 

Clilorine or bromide vapors 0001 .0004 

Muriatic acid 001 .005 

Sulphuric acid .005 

Sulphureted hydrogen .02 

Ammonia 01 .03 

Carbonic oxide 02 .05 

Carbonic acid 1.00 8.00 

Carbureted hydrogen 6.56 gr. 



the persons in the room may be more than sufficient 
to warm the room, which will necessitate providing 
for the removal of this heat from the room. 

Table XXIX gives the heat generated by differ- 
ent sources of illumination per candle power per 

hour. 

Generation of Heat by Ordinarily the heat given 
Illumination. off by electric lights is so 

small as to be incalculable, 
but where oil lamps, candles, or gas lights are used, 
the heat given oft* is appreciable, except in the case 
of the Welsbach burner, which gives off relatively 
a small amount of heat. The ordinary fish-tail 
burner is equal to about one and four-tenths square 
feet of radiation. 



Notes on Heating and Ventilation 1'^'^ 

In order that the air in a room occupied by hu- 
man beings may be reasonably pure it should be 
diluted with fresh air. The 

amount of the dilution, ex- Changes of Air Necessary, 
cept where chemical proc- 
esses are to be considered, is usually deter- 
mined by the per cent of carbon dioxide present, 
which is assumed to be proportional to the products 



Table XXIX— Heat Given Off by Illuminants. 

Total B. T. U.'s Heat radiated, 
Source. given off. B. T. U's. 

Gas— Fishtail burner 313 32 

Gas — Argand burner 198 28 

Gas — Welsbach burner 32 6 

Petroleum 158 42 

Incandescent lamp 14 10 

Arc lamp 2.5 



of respiration. - The carbon dioxide itself is not 
injurious, but it serves as an indication of the pres- 
ence of other injurious substances. It is usually 
assumed that carbon dioxide is uniformly distributed 
throughout the room. This, however, is not strictly 
true, as carbon dioxide is a very heavy gas and 
naturallv accumulates at the floor. Air that con- 
tains more than ten parts of carbon dioxide to each 
io,ooo parts of air produced by exhalation is of an 
unhealthful quality. Seven parts in io,ooo is ordi- 
narily considered the minimum limit of ventilation. 
The effects of poor ventilation are usually shown 
when the carbon dioxide exceeds six parts in 



178 Notes on Heating and Ventilation 

10,000 parts. The following rule may be used to 
determine the necessary amount of air that should 
be supplied to a room : Multiply the number of 
sources of carbon dioxide by the amount of carbon 
dioxide given off from each source. Multiply the 
result by 10,000 and divide by 4. This will give 
the mininuim amount of ventilation to be allowed 
per person. For satisfactory ventilation divide by 
3. Pure air is found to contain about 3 parts of 
carbon dioxide in 10,000. 

This may be expressed as follows : 

Let S=cu. ft. carbonic acid from each source per hr. 
n=number of sources. 
a=allowable limit of CO^ in cu. ft. of air. 
A=the cu. ft. of air to be supplied. 

Then A^=: 10,000 



a - 4 

a should not exceed 7 and a equals 10 is the sani- 
tary limit. 

For example, take a hall containing 400 adults, 
giving off (from Table XXVI) .58 cu. ft. of CO, 
per hour. Then to determine the amount of air 
necessary substitute in the above formula 

A=io,ooo "^^^ ^ ^ solving 

6-3 

A=77o,ooo cu. ft. per hour. 

The amount of air necessarv is usuallv deter- 
mined by allowing each person in the room so 



Notes on Heating and Ventilation 1'^^ 



Table XXX — Change of Air Necessary. 



Hospitals 3,600 cu. ft. per person 

Barracks and workshops 3,000 cu. ft. per person 

Schools 2,400 cu. ft. per person 

Churches, theaters & audience halls.2,000 cu. ft. per seat 

Office rooms 1,800 cu. ft. 

Toilet and bath rooms 2,400 cu. ft. per fixt're 

Dining rooms 1,800 cu. ft. per person 



many cubic feet of air per 

hour. The changes of air Ordinary Assumptions for 
ordinarily allowed are Change of Air. 

given in Table XXX . 

These figures in the above table give sufficient 
air so that the air in the room will remain contin- 
uously pure, even though occupied all the time. 
When less than these amounts are used there is dan- 
ger, if the buildings are very tight, that the rooms 
may become foul. The figures given above are sel- 
dom realized in practice, except where the fan sys- 
tem of ventilation is used. In school buildings using 
an indirect system the amount of air allowed per 
child seldom exceeds i,ooo cubic feet of air per 
hour. 

Another method that is sometimes used in figur- 
ing ventilation, particularly for smaller buildings, 
is to allow so many changes of air per hour. In 
rooms seldom occupied allow the air to be changed 
about once per hour. In living rooms about one 
and a half to two times per hour. In toilet rooms 



180 Notes on Heating and Ventilation 

four to five times per hour. In restaurants, where 
smoking is allowed, from five to six times per hour. 
In extreme cases the change of air is sometimes as 
high as ten times per hour. It is difficult, however, 
to change the air in a room very rapidly without 
producing drafts. 

The efifects of poor ventilation have been fre- 
quently tested in schools where for a short time the 

ventilation has been cut off. 

Effects of Poor The pupils at first complain 

Ventilation. of being cold, and it is found 

necessary to raise the tem- 
perature of the room from 70° to 80° before the 
occupants of the room are warm. This is no doubt 
due to the reduction in vitality owing to the im- 
purity of the air, and a lack of oxygen in the lungs. 
After the ventilation has been cut ofif for a period 
of from 20 to 30 minutes, the pupils begin to com- 
plain of headache. If the ventilation is cut ofif much 
longer it is necessary to dismiss some pupils on 
account of headache. 

For small residences and small buildings where 
it is not possible to go to any great expense for an 

elaborate system of ventila- 
Systems of Ventilation, tion, the best form of heat- 
ing giving adequate venti- 
lation is the hot air furnace. In large houses where 
it is not possible to apply the hot air system, the 
]:)est system is indirect radiators, either steam or hot 



Notes on Heating and Ventilation 181 

water. In still larger buildings where the flues have 
a large resistance and it is necessary to supply air 
in large quantities, the only feasible system of dis- 
tributing air is by mechanical means. The usual 
system employed is to draw the air through a 
series of steam coils into a tempered air chamber. 
In this chamber are located the fans. The fan or 
fans deliver the air through heating coils into the 
building. Systems similar to this have been used 
where the coils have been replaced by hot air 
furnaces. 

Systems of ventilation using mechanical draft 
give very satisfactory results if properly installed 
and allow of great latitude in the arrangement of 
the plant. Before taking up the details of the sys- 
tems of ventilation it is well to consider certain 
fundamental facts in the science of ventilation. 

The arrangement of inlet and outlet registers in 
a room should be given very careful consideration. 
They should be so placed as 

to avoid drafts and to insure Air Inlets and Outlets, 
uniform circulation through- 
out the room. Their position should be such that 
the air cannot pass directly from inlet to outlet flue. 
The creation of drafts may be avoided by bringing 
the air in at very low velocities, particularly where 
the air enters so as to strike the occupants of the 
room. The velocity passing through the registers 
should not exceed 200 feet per minute. Where the 



182 Notes on Heating and Ventilation 

air is brought in so that it cannot strike the occu- 
pants of the room the velocity of air through the 
registers may be as high as 400 feet per minute. 

The most satisfactory arrangement for most 
rooms is shown in Fig. 53. In this figure the inlet 




Figure 53. 



register is shown near the ceiling. The hot air 
leaving this register rises to the ceiling, passes 
along the ceiling to the cold window surfaces, where 
it is cooled and drops to the floor ; passes along the 
floor and out the vent flue. The inlet register is 
usually located about 8 feet above the floor and the 
outlet register from 4 to 6 inches above the floor, 



Notes on Heating and Ventilation 183 

just sufficient to avoid dust and dirt being swept 
into it. Where the current of air leaving the inlet 
register is liable to be centered in one point in the 
room it is well to put a diffusing register on the 
air inlet so that the air will be distributed in a num- 




Figure 54. 

ber of streams in dift'erent directions throughout 
the room. This arrangement of inlet and outlet 
registers is the usual one for school buildings. It 
is preferable to have the inlet and outlet register 
on the inside walls opposite the window surfaces 
and both registers on the same wall. This, how- 
ever, is not absolutelv necessarv. The inlet and out- 



184 Notes on Heating and Ventilation 

let registers should never be on the outside walls. 
Where the inlet register is placed on the floor and 
the outlet register at the ceiling then the air coming 
from the inlet register will pass directly to the outlet 
register and a large proportion of the heated air be 
lost ; in addition there will be very little circulation 
of air in the room, as shown in Fig. 54. 



1 



}}ft>?ff)ff}?>>f}ffff>f?fI}>}}>>I>>}?>}>??f>/>fM/))}ff^^}I}I>>f>I>f>?}>JH>>})>»»»)J»»}>f}}}>. 



•aasSi 



<j>r^jtjfj)jj>>)ij)j)}i J 




Figure 55. 



In rooms for restaurant purposes, where smoking 
is allowed or in smoking rooms or in kitchens, the 
air must be taken off the ceiling, as the foul air, 



Notes on Heating and Ventilation 185 

being warmer, rises to the ceiling. In this case it 
is necessary to bring the ventilating air in at the 
baseboard, at a very low velocity and at a large 
number of places and take the air out at definite 
points near the ceiling, as shown in Fig. 55. In 
theaters and churches special means must be em- 
ployed for securing ventilation. It is customary to 
admit the air in a large number of places. Some- 
times this is done by means of a large number of 
small registers placed directly under the seats. 
Care, however, must be used in doing this to avoid 
drafts. Another method is to employ a large num- 
ber of openings around the sides of the room. The 
air is usually taken ofif near the stage at the lowest 
point in the auditorium. There should be provided 
in all auditoriums some means of taking the air off 
the ceiling, as oftentimes the heat given off by the 
occupants of the room is more than sufficient to 
heat the room, and in addition we have the heat 
given off by the sources of illumination. This heat 
can be best taken care of at the ceiling line, which 
is naturally the warmest point in the room. 



CHAPTER X. 



DESIGN OF HOT AIK HEATING SYSTEM. 

In a hot air furnace the cold air from the outside 
is passed over heated iron surfaces, usually en- 
closed in galvanized iron or 

Design of Hot Air brick walls. The space be- 
System. tween the walls and hot sur- 

faces of the furnace is con- 
nected to the outside air at the bottom and at the 
top to the flues leading to the rooms. The 
amount of air circulating through the furnace will 
depend upon the temperature of the hot air leaving 
the furnace and the height and resistance of the 
flues. In order that the air in a room may be 
quickly replaced by w^arm air it is necessary that 
the room be provided with a foul air flue. 

A great many of the difficulties that have been 
experienced with the hot air system as ordinarily 
installed are due to the sharp competition in busi- 
ness, which has resulted in the erection of plants 
of inferior workmanship and design. One of the 
commonest mistakes is the installation of a furnace 
much too small to do the work properly. The 
result of putting in a small furnace is that the fire 
must be continually crowded so that the heating 
surface is at high temperature and a large amount 



Notes on Heating and Ventilation 1^7 

of the heat of the coal is wasted in excessive stack 
temperature. 

The hot air system with natural draft should 
not be used in houses where the horizontal por- 
tion of the hot air flues would exceed 20 feet in 
length. In very large houses two or more furnaces 
may be used to avoid excessive pipe resistance. 

Hot air furnaces are as varied in types as are 
steam boilers. They are made either of cast iron 
or steel. It is difficult to de- 
cide between the merits of Hot Air Furnaces, 
these two materials. Cast 

iron is less liable to be rapidly deteriorated by rust 
when the boiler stands in the summer, but it is 
more easily broken either by misuse or shrinkage 
strains in the castings. There is no essential differ- 
ence between the metals in their conducting ca- 
pacity as applied in these furnaces. 

It is very important to see that the furnace is 
so constructed that the joints between the fire-box 
and hot-air chamber are tight, so that the air en- 
tering the rooms may not be mixed with gases of 
combustion. This is one of the most difficult things 
to prevent in the hot air furnace. Joints should be 
as few as possible and vertical joints should be 
avoided. The introduction of moisture into the 
air passing through the furnace is an important 
consideration and will be treated in a separate para- 
graph. 



188 Notes on Heating and Ventilation 

The builders rate their furnaces at about their 
maximum capacity. The rating being expressed as 
the number of cubic feet of building volume the 
furnace will heat. In selecting a furnace it is wise 
to have 25 to 50 per cent excess capacity in the fur- 
nace over the builder's rating. 

In the hot air furnace we have the fire and hot 
gases on one side of the shell and air on the other 
side of the shell. Air being a poor medium for the 
conduction of heat it is essential to economy that a 
hot air furnace should have large heating surfaces 
in proportion to grate area. The best manufac- 
turers allow from 50 to 70 square feet of heating 
surface per square foot of grate surface. 

A furnace should be provided with some form 
of shaking and dumping grate which is easily 
cleaned. In addition to draft doors admitting air 
below the grates, the furnace is usually provided 
with a check damper in the smoke pipe. The draft 
door and check damper are arranged so that they 
may be controlled by chains situated in some con- 
venient point in the room above. 

It is very important that air after being heated 
by the furnace pass over the surface of a pan of 

water so that it can 

Necessity of Supplying Mois- take up moisture. One 

ture to Heated Air. pound of air at 2)^'' F. 

will hold in the form 
of a vapor .003 of a pound of water, and at 150 de- 



Notes on Heating and Ventilation 189 

grees it will hold .22, or about 70 times as much. 
If then we take air saturated with moisture at an 
outside temperature of 32 degrees and heat it up 
to 150 degrees we have increased its capacity for 
moisture 70 times. On entering the rooms if the 
air has not been given opportunity to take up mois- 
ture it will take it up from the objects in the room. 
This drying effect of the air injures the furniture 
and woodwork and affects the persons occupying 
the room, producing a dry throat and a feeling of 
cold due to rapid evaporation from the skin. 

The usual method of overcoming this is to have 
a pan filled with water situated in the furnace near 
the fire-box. This, however, is the wrong end of 
the furnace to place the pan, as the air entering is 
coolest at this point. The water should be added 
to the air as it leaves the furnace. In some hot air 
installations every pipe leaving the furnace has a 
trough in it, which is filled with water, and from 
this water the air takes up its moisture. 

The cold air supplied to the furnace is usually 
taken from one of the basement windows and 
brought to the furnace 
through a tile or w^ooden Cold Air Duct, 

duct lined with galvanized 

iron ; where a tile duct is used it is placed below 
the level of the cellar floor. The cold air should be 
taken from the side of the house that is subject to 
the prevailing winds. It is sometimes desirable to 



190 Notes on Heating and Ventilation 

have cold air ducts leading to different sides of the 
house, so that the supply of cold air may be taken 
from the windiest side. 

It is well to provide some means of recirculation 
of the air in the house through the furnace. The 
air for recirculation is usually taken from the hall. 
If it is desired to recirculate partially and take the 
balance of the air from outside, the recirculating 
pipe should be brought to the furnace separately, 
and a deflecting plate placed in the air space under 
the furnace. If this is not done the air will come 
in from the outside and pass up the recirculating 
pipe instead of going to the furnace. If, however, 
the recirculating pipe is only to be used when the 
cold air pipe from outside is closed, then the re- 
circulating pipe can be conducted into the cold air 
pipe directly. In this case the cold air pipe and 
recirculating pipe must both be provided with 
dampers. The cold air pipe should have at least 
three-fourths of the combined areas of the hot air 
pipes. 

It is a common error to make the recirculating 
pipe of a furnace system too small. The recircu- 
lating pipe should be not less than three-fourths 
the area of the cold air pipe. It is better to have it 
equal in area to the cold air pipe. 

The furnace should be centrally located, or if the 



Notes on Heating and Ventilation 1^1 

coldest winds come from a certain direction, it can 
be located more on that side 
of the house from which the Hot Air Flues, 

cold winds come. The hot 

air flues leading from the furnace should be as short 
and direct as possible ; long horizontal pipes should 
be avoided. Horizontal pipes should pitch sharply 
towards the furnace, three-quarter inch to the foot 
is good practice. All hot air pipes should have 
nearly equal resistance to the passage of the air. 
The hot air flues should have as few and as easy 
turns as possible. They should never be placed in 
the outside walls. Uptake flues of any kind in out- 
side walls seldom draw satisfactorily. The hot air 
flue should enter the room in most cases opposite 
the largest exposed glass surface or some distance 
from it. The circulation of air in the room would 
be best if the hot air entered near the ceiling. The 
principal objection to this is that the registeY in the 
wall is apt to blacken the wall and it does not allow 
people to warm themselves over it. Floor regis- 
ters are very objectionable as they always serve as 
receptacles for all kinds of rubbish and sweepings. 
Dampers should be provided in all pipes leading 
to rooms above the flrst floor. If all the registers 
are provided with dampers there is danger of burn- 
ing the furnace, due to shutting oft all the passages 
for removing hot air and preventing circulation in 
the furnace. It is good practice to have no valve 



192 Notes on Heating and Ventilation 

in the hall register so one pipe will always be open. 

The velocity of air for first floor pipes may be 

calculated as three to four feet per second, second 

floor four to five feet per 

Proportions of Hot Air second, third floor and floors 

Flues. above five to six feet per 

second. 

The registers should be proportioned so as to give 

a velocity of two to three feet per second on the 

first floor and three to four feet per second on the 

floors above. The effective area of the ordinary 

register is about 50 per cent of the actual area, 

taking outside dimensions. 

H. B. Carpenter, in a paper before the Society 
of Heating and Ventilating Engineers (Transac- 
tions, vol. 5, p. "jy), gives the following rule for 
finding the cubic feet of air passing through pipes 
per minute : 

To the first floor multiply the area in inches by 

1.25. 

To the second floor multiply the area in inches 

by 1.66. 

To the third floor multiply the area in inches by 
2.08. 

It is good practice to figure on changing the air 
in the principal rooms five times per hour in hot air 
heating. 

The foul air flues should be placed in the inside 



Notes on Heating and Ventilation 198 

walls and with foul air registers at the baseboard. 

The reason being that the 
hot air entering the room Foul Air Flues, 

opposite the window sur- 
faces rises to the ceiling, passes along the ceiling to 
the windows and is cooled. It then drops to the 
floor line, passes along the floor and out the foul 
air register. The hot air register should be a suf- 
ficient distance from the foul air register so that 
the hot air will not pass directly to the foul air flue. 
A cheap foul air flue can be made by having a reg- 
ister in the baseboard opening into the spaces be- 
tween the studs, selecting a space that is open to 
the attic, a ventilator is placed on the attic space 
and discharges foul air out of doors. No two rooms 
should open into the same studding space. A still 
better draft can be produced by extending each flue 
separately by galvanized iron pipe to the ventilator. 
If no ventilating flues are provided, it is very diffi- 
cult, especially if the house is tight, to get a proper 
circulation of hot air from the furnace ; you cannot 
put hot air into a room if there is no provision for 
taking cold air out. 

A fireplace makes one of the best forms of foul 
air flue. In a house well provided with fireplaces, 
it is often not necessary to provide any other foul 
air flues. 

The size of the hot air flue, vent flue, hot air 



194 Notes on Heating and Ventilation 

register, heating surface and grate surface in the 

furnace is given in Table 
General Proportions of ^wt o-i • ^ t^i • 

Hot Air System. ^^^^' ^his table is given 

for rooms of average pro- 
portion and under average conditions. 



Table XXXI — Proportions of Hot Air Heating System. 
Contents of Room ix Cu. Ft. 500 1,000 1,500 

First Floor — 

Diameter hot air flue, in 6 8 9 

Diameter foul air flue, in 8 9 

Second P'loor — 

Diameter hot air flue, in 6 7 S 

Diameter foul air flue, in 6 8 9 

Grate area in furnace, sq. in 25 50 75 

Heating surface in furnace, sq. ft.... 10 20 30 

2,000 2,500 3,000 3,500 4,000 5,000 6,000 8,000 10,000 

10 11 12 13 14 16 17 20 '24 
10 11 12 13 14 16 17 20 24 

9 10 11 11 12 14 15 18 20 

10 11 12 13 14 16 17 20 24 

100 125 150 175 200 250 300 350 400 

40 50 60 70 80 100 125 160 200 



The following assumptions have been made in 
the above table : Temperature outside air, o de- 
gree ; temperature of air in the room, 70 degrees ; 
changes of air in the room, three times per hour. 

Velocity of air in hot air flues, ist floor, 3 ft. per 
second. 

Velocity of air in hot air flues, 2nd floor, 4 ft. per 
second. 

Velocity of air in foul air flues, istand 2nd floors, 
3 ft. per second. 



Notes on Heating and Ventilation 195 

Temperature of air entering the room, i6o de- 
grees. 

Proportion of grate surface to heating surface, i 
to 60. 

Pounds of coal burned .per square foot of grate 
surface per hour, 2.5. 

The temperature of the rooms should be regulated 
by the drafts of the furnace as much as possible. 
The heating surfaces of 

the furnace should never Suggestions for Operating 
be brought to a red heat. Hot Air Furnaces. 
If it is necessary to do this 
to keep the rooms warm, the furnace is too small. 

Ashes should be frequently removed from the 
furnace, as an accumulation of ashes may burn out 
"the grate. Never shake the fire more than is neces- 
sary to expose the red coals to the ash pit. The 
furnace should be cleaned at least once a year. The 
water pan of the furnace should be kept full of 
water. 

ROUGH RULES FOR HOT AIR SYSTEM. 

. I. The volume of the house divided by 50 equals 
square feet of heating surface in furnace radiator. 

2. The volume of the house divided by 20 equals 
the number of square inches of grate area in the 
furnace. 

3. Divide the volume of the room by 20 and the 
square root of the quotient wall be the diameter of 



196 Notes on Heating and Ventilation 

the furnace pipe for the first floor room. For sec- 
ond floor rooms divide the volume by 25 and the 
square root of the quotient will be the diameter of 
the furnace pipe. 

As an example of the hot air system applied to 
the ordinary dwelling, take the same house that was 

used as an example of di- 

Example of Hot Air rect steam heating. The 
System. heat lost from the rooms 

would be the same as in 
the case of direct steam. As an example of an in- 
dividual room take the parlor. 

From Table XII we see that the volume of the 
parlor is 1,665 cubic feet and the heat lost 10,395 
B. T. U's per hour. In figuring the heating system 
for the parlor the following assumption will be 
made: The hot air enters the room at 160°. Cold 
air enters the furnace at 0°. The temperature in 
the room is 70°. Then the air entering the room is 
reduced in temperature 160 — 70^=90°. Each pound 
of air on having its temperature reduced 90° would 
give up .2375X90=21.4 B. T. U's. Then there 
will have to be introduced into the room to supply 
heat lost from the room 10,395-^21.4=485 pounds 
of air per hour. At atmospheric pressure a pound 
of air occupies approximately 13 cubic feet, hence 
485 pounds of air is equal to 6,300 cubic feet. This 
is the amount of air which must be delivered to the 
room per hour; 6,300 cubic feet of air per hour is 



Notes on Heating and Ventilation 197 

equal to 1.75 cubic feet per second. Allowing a 
velocity of 3 feet per second, the area of the pipe 
would be i.75^-3=.58 square feet, which is equiva- 
lent to 84 square inches, or approximately the area 
of a pipe 10.5 inches in diameter. To warm the 




First Floor. 

Parlor 1,665 10,395 18,500 6,300 10 Vg 

Sitting room 2,100 7,035 12,500 4,350 9 

Dining room 1.640 7,350 12,800 4,500 9 

Kitchen 1,610 10,300 18,000 6,250 IO1/2 

Hall 1,210 7,035 12,500 4,350 9 

Second Floor. 

W. chamber 1,320 10,050 17,900 6,200 9 

Alcove 810 7,560 13,400 4,750 8 

S. chamber 1,560 7,035 12,500 4,400 8 

N. Chamber 1,440 7,455 13,300 4,650 8 

Bath 410 3,150 5,600 1,850 6 

E. chamber 880 5,250 9,400 3,300 7 

Halls 88 2,730 4,800 1,750 6 



151,200 



air going to the parlor would require 485 X -2375 X 
160=18,500 B. T. U's. In a similar way the same 
quantities have been calculated for the other rooms. 
Except that for the second floor room, a velocity of 
4 feet per second has been allowed. 

Column 3 of Table XXXII shows the heat which 
is left by the air in the room. Column 4 shows the 



198 Notes on Heating and Ventilation 

heat used to warm the air entering the room. The 
difiference between these two cohimns is the heat 
lost up the ventilating flues. This loss should not 




l^'W** 



Figure ."iO. 



be charged against the hot air furnace, but should 
be considered as the loss that nnist be charged to 
ventilation. The loss is about 44 per cent if the 



Notes on Heating and Ventilation 199 

temperature of the outside air is at o° and the tem- 
perature of the air entering the room is 160'^. As 
the temperature of the outside air or the incoming 
air is increased proportionately more heat enters 
the room and this loss becomes less. During the 
average winter weather the outside air is 35°, in 
which case the per cent of loss by ventilation, that 
is, through the ventilating flues, is about 30 per cent. 
Summing up column 4 of the table gives the heat 
required to warm the air entering the entire house 
in zero weather or 151,200 B. T. U's. If we assume 
that 80 per cent of the coal goes into the heated air, 
then there will be required from the coal 151,200-^ 
.8=188,500 B. T. U's per hour. A good anthracite 
coal contains about 13,500 B. T. U's; then in zero 
weather this house would use 1 88, 500-f- 13,500=14 
pounds of coal per hour. As the average loss from 
a house during the heating season is approximately 
50 per cent of the loss during zero weather, the 
A\'erage consumption of coal in this house for the 
heating season would be i4X.5^7-00 pounds of 
coal per hour. Assuming the furnace to be oper- 
ated 24 hours per day and 200 days per year, the 
coal consumption for this house would be 7X24X 
200-^-2,ooo-=i6.8 tons. Fig. 24 shows a cross sec- 
tion of a house with the hot air system installed. 



CHAPTER XI, 



FAN SYSTEM OF HEATING. 

Where it is necessary to introduce large quanti- 
ties of air into a building for the purpose of venti- 
lation a natural system of circulation is out of the 
question and it is necessary to force the air into the 
building by some mechanical device. This is usually 
done by means of a steel plate blower which delivers 
the air with sufficient pressure to force the air into 
all rooms in the building. The pressure required in 
the average building does not usually exceed one- 
quarter ounce. The mechanical system of ventila- 
tion has the additional advantage that its operation 
is entirely independent of the heating of the build- 
ing: and the building mav be ventilated as easily in 
the summer as in the winter. The natural system 
of ventilation depends entirely upon the air in the 
flues being heated, and during the summer periods 
the system is inoperative. 

There are two general schemes of fan heating, 
one in which the air is heated to a temperature 

higher than that in the 

Systems of Fail Heating, room, so that it furnishes 

enough heat to supply the 
heat lost from the walls and windows, as well as to 



Notes on Heating and Ventilation '^01 

furnish air for ventilation. In the other system the 
heat loss from walls and windows is supplied by 
direct radiation situated in the room and the fan 
supplies only the necessary amount of air for venti- 
lation. In the latter system the air for ventilation 
is supplied at about the temperature to be main- 
tained in the room. The first system, in which all 
the heat is supplied by means of a fan, is most ap- 
plicable in buildings that must be heated and venti- 
lated both night and day. Hospitals and asylums 
are buildings of this class. It has certain disad- 
vantages, however. When a room lias very large 
glass surfaces it is almost impossible with this sys- 
tem to prevent strong cold drafts coming down 
along the window surfaces. The system is in many 
cases wasteful. In order to heat a building it is 
often necessary to admit more air than is required 
for the purpose of ventilation, and all the heat 
put into the air to raise the temperature of the out- 
side air to the temperature of the room is lost. On 
the other hand, this system requires but one system 
of heating, which makes it less expensive to install. 
The second system mentioned, where direct ra- 
diation and a fan are both used, is most applicable 
in buildings that require ventilation only part of the 
time. Schools, factories, oflfice buildings are build- 
ings that may be included in this class. While the 
buildings are filled with occupants the fan system is 
operated; as soon as the occupants leave the build- 



202 Notes on Heating and Ventilation 

ing the fan system is closed and the building kept 
warm by means of direct radiation. The building 
is thus kept warm at a minimum expenditure for 
fuel. There is no necessity of introducing into the 
building more air than is necessary for ventilation. 
But the system is expensive to install, as it involves 
installing two separate systems of heating. This 
system is being more and more favorably consid- 
ered, however, in connection with the class of build- 
ings mentioned. 

The usual arrangement of the fan system is 
shown in Fig. 57. The air is drawn first through 

a series of tempering coils 

General Arrangement of shown at A. Then it enters 

the Fan System. a tempered air chamber in 

which is located the fan. 
This delivers the air through a series of heating 
coils B into the hot air chamber. From this hot 
air chamber the individual rooms in the buildings 
take their heat. The tempered coils are usually 
designed to heat the air to about 70°. The fan 
takes this air at 70° and passes it to the heating 
coils. After leaving the heating coils the tempera- 
ture of the air is from 130° to 140°. Where the 
air is used for ventilation only the heating coils are 
omitted and the air is delivered by the fan from the 
tempered air chamber directly to the room. 

The quantity of air to be supplied to each room 



Notes on Heating and V^entilation 203 

will depend upon the system of heating employed. 
If the heating is done en- 
tirely by fan enough air Quantity of Air to Be 
must be admitted so that the Supplied, 

heat left by the air will be 

sufficient to heat the room. In audience and school 
rooms the amount of air necessary to supply proper 
ventilation is usually sufficient for heating. In of- 




Figure 57. 

fices and living rooms more air will have to be sup- 
plied in order to heat the room than would be neces- 
sary for purposes of ventilation. Roughly speak- 
ing, if the number of cubic feet of air supplied to 
the room per hour is four times the cubic contents 
of the room the room wtU be heated, providing the 
air be supplied at not less than 140°. In a system 
where direct radiation is used to supply losses from 



'^0.4 Notes on Heating and Ventilation 

walls and windows only enough air is introduced 
to supply the necessary ventilation. The amount 
of air necessary can be determined by rules pre- 
viously given under the head of Ventilation. 

In most cases the type of fan known as the steel 
plate blower is best adapted to the w^ork of fan 

heating. The theory of this 

Size, Speed and Horse- fan has been discussed by 

power of Fan. Weisbach and Lindner in 

their treatises, also by vari- 
ous writers in the Transaction of the Society of 
Heating and Ventilating Engineers. The results 
derived are difficult of application. The following 
general statement may be made, however. The 
discharge capacity of a fan depends upon the speed 
of the fan tips, the size of the fan blades, and the 
size of the discharge openings. As the discharge 
opening of the fan is decreased the velocity of the 
air leaving the fan increases and the pressure of air 
in the fan case increases until we get to the maxi- 
mum pressure that can be produced by a certain 
velocity of fan tips. This will occur when the area 
of the outlet equals the effective area of the fan 
blades. This is the point at which the fan delivers 
the maximum amount of air corresponding to the 
pressure for a given speed. If we further reduce 
the discharge outlet the pressure in the fan case 
remains constant, the quantity of air discharged is 
reduced and the power to drive the fan is reduced. 



Notes on Heating and Ventilation 



205 



The theoretical relations connecting the pressure 
of the air, the quantity of the air delivered, power 



Table XXXIII — Fan Capacities. 

Speeds, Capacities and Horse Powers of ''A B C' Steel Plate 
Fans of Varying Revolutions. 



R.P.M. 


FAN 


60 


60 


70 


80 


90 


100 


110 


120 


140 


160 


180 


200 


220 


240 




PerV, 


785 


942 


1100 


1257 


1414 


1571 


1728 


1885 


2200 


2513 


2837 


8141 


3455 


8769 




AirV. 


685 


820 


957 


1092 


1230 


1367 


1503 


1640 


1,P15 


2182 


2459 


2732 


8005 


8279 


100 


Pres. 


.017 


.025 


.034 


.044 


.0,55 


.068 


.082 


.100 


.134 


.175 


.231 


.273 


.385 


.401 




Cu. Ft. 


682 


1121 


1,870 


2652 


3840 


5475 


6395 


9565 


14916 


21750 


80221 


4t608 


55201 


71941 




H. P. 


.150 


;222 


.370 


.476 


.672 


1.01 


1.37 


2.03 


3.46 


5.47 


7.7 


12.0 


17.1 


25.1 




Per V. 


981 


1178 


1375 


1571 


1768 


1964 


2160 


2356 


2750 


3141 


8533 


3926 


4318 


4711 




AirV. 


853 


1025 


1196 


1366 


1538 


1707 


1879 


2029 


2390 


2724 


3073 


3415 


8756 


4098 


125 


Pres. 


.027 


.089 


.053 


.060 


.039 


.108 


.132 


.153 


.212 


.276 


.350 


.435 


..525 


.626 




Cu. Ft. 


852 


1402 


2338 


31.58 


4809 


6844 


7992 


11945 


18645 


27170 


87767 


52010 


68997 


99910 




H. P. 


.175 


.284 


.439 


.588 


.934 


1.34 


2.06 


2.90 


5.00 


8.15 


12.5 


19.3 


29.2 


43.5 




PerV. 


1177 


1413 


1650 


1886 


2121 


2356 


2592 


2827 


3S0O 


3770 


4240 


47U 


5182 


5653 




Air V, 


1025 


1230 


1432 


1640 


1845 


2044 


2255 


2460 


2870 


3280 


3688 


409a 


4500 


4928 


150 


Pres. 


.039 


.056 


.075 


.100 


.180 


.160 


190 


.230 


.800 


.400 


.503 


.626 


.758 


.904 




Cu. Ft. 


1023 


1681 


2805 


3979 


5760 


8110 


»S0 


14360 


22374 


32610 


45325 


62412 


82811 


10812C 




H. P. 


.200 


.325 


.531 


.756 


1.27 


1.86 


'2.34 


3.£0 


7.22 


11.3 


19.6 


32.1 


46.2 


68.6- 




PerV. 


1374 


1649 


1925 


2200 


2474 


2749 


3024 


•3297 


38.50 


4380 


4947 


5496 


6046 


6596 




AirV. 


1195 


1434 


1674 


1914 


2152 


2390 


2630 


2868 


3S50 


8826 


4303 


4781 


5260 


574? 


175 


Pres 


;053 


.076 


.104 


.134 


.172 


.212 


.258 


.^06 


.420 


.554 


.687 


.848 


lj02 


1.21 




Cu Ft. 


1194 


1962 


3274 


4622 


6729 


9594 


11200 


16715 


26100 


38043 


52883 


72814 


96626 


126089 




H.-P. 


.225 


.393 


.647 


1.01 


1.74 


2.46 


3.55 


5.52 


9.91 


17.3 


27.9 


44.2 


67.1 


103.0 




PerV. 


1570 


1884 


2200 


2511 


2828 


3142 


3456 


8770 


4400 


5026 


56.54 


62^ 


6910 


7538 




AirV. 


1366 


1640 


1915 


2187 


2460 


2737 


3007 


3280 


38S0 


4375 


4918 


5465 


6011 


6558 


200 


Pres. 


.069 


.101 


.1.34 


.175 


.?i5 


.274 


.333 


.392 


.537 


.700 


.f03 


1.12 


1.34 


J159 




Cu. Ft. 


1364 


2242 


3740 


5304 


7690 


10960 


12830 


19150 


29850 


43520 


•60442 


83331 


110422 


143902 




HP. 


.262 


.478 


.855 


1.26 


2.05 


3.16 


4.69 


7.01 


13.3 


23.7 


39.2 


62.1 


96.6 


154.5 




Per V. 


1766 


2120 


2475 


2829 


3182 


3534 


8888 


4241 


4950 


5654 


6360 


7065 


7774 






AirV. 


1536 


1844 


2153 


2459 


2767 


S073 


3383 


8688 


4305 


4919 


5533 


6148 


6762 




225 


Pres. 


.037 


.126 


.172 


.225 


.285 


.351 


.421. 


.507 


.690 


.601 


1.14 


1.41 


1.60 






Cu. Ft. 


1534 


2523 


4207 


5969 


8655 


12334 


14385 


21500 


33560 


48680 


68000 


93634 


124217 






H. P. 


.300 


.581 


1.03 


1.57 


2.61 


4.09 


5.95 


9.29 


17.0 


31.1 


52.8 


87.9 


142.5 






PerV. 


1963 


2355 


2750 


3143 


3535 


3927 


4320 


4712 


5.500 


6283 


7067 


7852 








Air V, 


1708 


2048 


2392 


2734 


8070 


3416 


37.58 


4100 


4780 


54.50 


6148 


6840 




250 


Pres. 


.109 


.056 


.213 


.280 


..360 


4.30 


.520 


.630 


.860 


1.12 


1.48 


1.73 






Cu. Ft. 


1706 


2793 


4675 


63.32 


9600 


13705 


16000 


23950 


37310 


5420O 


75558 


104036 






H. P. 


.375 


.684 


1,22 


1.79 


3.32 


4.97 


744 


11.6 


22.5 


41.2 


71.7 


121.4 






PerV. 


2159 


2.591 


3025 


3457 


3889 


4319 


4731 


5183 


6050 


6911 


7774 








AirV. 


1878 


22.58 


2632 


3008 


3383 


3755 


mo 


4.507 


5263 


6013 


6763 




275 


Pres. 


.131 


.189 


»258 


.337 


.426 


.526 


.623 


.7.56 


1.04 


1..35 


1.71 






Cu. Ft. 


1876 


3083 


5142 


7294 


10578 


15773 


17394 


26278 


41020 


58328 


83104 






H. P. 


.436 


.821 


1.45 


2.35 


3.92 


6.09 


9.09 


14.5 


29.4 


54.7 


89.3 






PerV. 


2355 


2826 


3300 


3771 


4242 


4712 


5184 


5654 


6600 


7539 








AirV. 


20.50 


24.58 


2875 


3280 


3685 


4100 


4510 


49E0 


.5745 


6555 




300 


Pres. 


:160 


.'^25 


.302 


.401 


..520 


.630 


.760 


.910 


1.26 


1.62 






Cu. Ft. 


20 »6 


3363 


5610 


7957 


11520 


162.50 


19200 


28800 


44750 


63629 






H. P. 


.500 


.975 


1.73 


2.86 


4.63 


7.44 


11.4 


181 


37.5 


69.3 






PerV. 


2747 


3297 


3850 


4399 


4949 


5447 
4770 


6018 


6597 


7700 








AirV. 


2390 


2863 


3345 


3827 


4-295 


^262 


5724 


6680 


NOTE 


850 


Pres. 


.216 


.306 


.418 


.550 


.693 


.8.50 


.970 


1.25 


1.68 


These figures guaraiiteed to 




Cu Ft. 


2387 


3923 


6545 


9282 


13410 


19110 


22395 


33400 


52206 




H. P 


.663 


1.28 


2.38 


3.89 


6.65 


10.7 


17.2 


28.3 


55.8 


be correct with the resistance 




PerV. 


3140 


3768 


4400 


5028 


5656 


6282 


6912 


7540 




ordinarily found in heating 




AirV. 


2732 


3278 


3830 


4374 


4926 


.5470 


6013 


6560 


work. 


400 


Pres. 


.277 


.399 


.546 


.713 


904 


1.14 


1.42 


163 






Cu. Ft. 


2729 


4384 


7480 


10620 


15400 


219.50 


25574 


38300 






H. P, 


750 


170 


3.19 


5.04 


9.S4 


15.3 


25.2 


39 2 





206 Notes on Heating and Ventilation 

to drive the fan and the speed can be stated briefly 
as follows : The quantity of air delivered is pro- 
portional to the peripheral velocity of the fan tips 
and to the area of the fan tips. The pressure pro- 



Table XXXIV — Fan Efficiency Under Varying Pressures. 

Speeds, Capacities and Horse Powers of "A B C" Steel Plate 
Fans of Varying Pressures. 



PRESSURES. 


Hot- 


H oz. 


Koz. 


1 oz. 


IH oz. 


IH oz. 


IKoz. 


2 02. 


2!4 oz. 


3 oz. 


50 


CU. FT. 

R. P. M. 

H, P. 


2740 
»S0 

.80 


3900 
.540 


4760 
659 
2.66 


5490 
760 
385 


6090 

847 
5 32 


6700 
9:^0 
6.65 


7350 
1004 

8.22 


7750 
1075 
10.25 


8650 
1200 
14.38 


9520 
1320 

18.85 


60 


CU. FT 

R. P. M. 

H. P. 


S.i.'iO 
317 
1.03 


5040 
449 
2.05 

7350 
383 
3.02 


5490 
549 
3.42 


7100 
4.95 


7910 
706 
6.84 


8700 
776 
8..54 


9410 

838 
10.6(> 


10200 
895 
13.2 


11210 
1000 
18.45 


12330 
1100 
24.3 


70 


CU. FT. 

R. P. M. 

H. P. 


5220 
271 
1.51 

630 
238 
1.82 

7850 
211 
2.27 


90.)0 
471 
5.04 


10400 
.542 
7.30 


11600 

605 

10.10 


12700 

663 

12.80 


13750 

716 

15.60 


147.50 

768 

19.40 


16.500 

857 

27.20 


18000 
938 
85.7 


80 


CU. FT. 

R. P M. 

H. P. 


8800 
S36 
3.65 


10940 
412 
6.08 


125.50 
474 

8.82 


14000 
12.15 


15350 

580 

15.20 


16600 
627 

18.85 


17300 

672 

23.40 


19890 
. 750 

saf.80 


21920 

825, 
43.2 


90 


CU. FT. 

R. P. M. 

H. P. 


11050 
299 
4.53 


13600 
366 
7.56 


15600 

421 

11.00 


174.50 

470 

15.10 


19100 

515 

18.90 


206.50 

557 

23.40 


22100 

596 

29.10 


247.50 

666 

40.70 


27300 
734 
53.5 


100 


CU. FT. 

R. P. M. 

H. P. 


a-uo 

190 
2.76 


13.500 
268 
5.52 


16500 
329 
9.20 


19050 

380 

13.35 


21300 

424 

18.42 


23200 

464 

23.00 


25200 

502 

28.60 


27000 

537 

35.10 


30500 

600 

49.60 


33000 
659 
65.2 


110 


CU. FT. 

R P. M. 

H. P. 


11870 
173 
3.43 

15030 
159 
4.32 

19800 
i:« 
5.72 

.250-)0 
118 
7.29 


16700 
244 

6.85 


20600 

300 

11.44 


23600 

345 

16.60 


26400 

885 

22.J,0 


28900 

422 

28.60 


31300 

4r)6 

35.50 


33500 

488 
44.00 


37500 
546 
61.7 


41200 
600 
81.2 


120 


CU. FT. 

R. P. M. 

H. P. 


21000 
224 

8.65 


2.5840 

274 

14.40 


29700 

316 

20.t0 


33200 

3.54 

28.80 


36400 

387 

36.00 


39400 

418 

44.60 


42200 
448 

55.45 


47100 
.500 

77.7 


51800 

5.50 

102.1 


140 


CU. FT. 

R. P. M. 

H. P. 


27900 

192 

11.42 


34200 
2:» 

io.oo 


39400 

271 

27.60 


44000 

302 

38.10 


48200 

331 

47.60 


51200 

357 

59.00 


55800 

88;i 

73.30 


639C0 

43<.l 

1027 


68400 

470 

1S5.5 


160 


CU. FT. 

R. P M 

H. P 


35600 

168 

14.60 


43700 

206 

24.32 


50250 

237 

35.20 


56150 
265 

48.60 


61500 

290 

160.75 


66500 

314 

75.20 


71250 

336 

93.50 


79200 

373 

134 


87500 

412 

172.0 


180 


CU. FT. 

R. P. M. 

H. P. 


31410 
106 

9.07 


44200 

149 

18.13 


54300 

183 

30.24 


62700 

211 

43.80 


69700 

235 

60.48 


76700 
259 
75.5 


82700 
279 
93.6 


88400 

298 

116.20 


9V000 

S34 

131.0 


108400 

966 

214.0 


200 


CU. FT. 

R. P. M. 

H. P 


38000 

95 

11.02 


53700 

134 

22.20 


66000 

165 

36.80 


75700 
189 
53.3 


849.50 
212 
73.5 


93000 
232 
92.0 


loaioo 

251 
114.0 


107':00 

268 

141.5 


120000 

300 

198.5 


134000 

390 

261.0 


220 


CU. FT. 

R. P. M. 

H. P. 


46800 

87 

13.48 


66300 

1-23 

27.00 


80600 

150 

44.90 


93200 

173 

65.10 


104000 
193 
89.6 


113500 

211 

112.0 


1-28300 

229 

139.0 


131400 

244 

173.0 


147100 

274 

243.0 


161500 

300 

818.0 


240 


CU. FT. 

R. P M. 

H. P. 


56400 

80 

16 10 


79000 

112 

32.30 


96.500 

137 

.5:j.mo 


112000 

159 

7S00 


124800 

177 

107 4 


i:i8S00 

194 

1:m.O 


147400 

209 

1660 


1.58000 

?-'4 

206.0 


176100 

250 

290.0 


194000 

275 

S82.0 



Notes on Heating and Ventilation 207 

duced is proportional to the square of the peripheral 
velocity of the fan tips and the power necessary is 
proportional to the cube of the peripheral velocity 
of the fan tips and to the quantity of air delivered. 
Mr. M. C. Huyett gives the following approxi- 
mate rule for finding the capacity of a fan : The 
quantity of air in cubic feet delivered per revolu- 
tion is equal to one-third the diameter of the fan 
wheel multiplied by the width of the blades at cir- 
cumference, multiplied by the circumference of the 
fan wheel. All dimensions expressed in feet. 

Professor R. C. Carpenter gives the. following 
rule for determining the horsepower required by 
the fan : The horsepower required for the fan is 
equal to the fifth power of the diameter of the fan 
wheel in feet multiplied by the number of revolu- 
tions per second, divided by 1,000,000 and multi- 
plied by one of the following coefficients — for free 
delivery, 30; for delivery against i-ounce pressure, 
20; for delivery against 2 ounces pressure, 10. The 
best method of obtaining the horsepower to drive 
a fan and the capacity of the fan is by reference to 
the blower companies' catalogues. Some companies 
have published catalogues which are obviously 
wrong. At the present time, however, the Ameri- 
can Blower Company, of Detroit, have published in 
their catalogue tables that are very satisfactory. 

Table XXXIII gives the speed, capacity and 
horsepower required for various sized fans. 



208 Notes on Heating and Ventilation 

Table XXXIV gives similar results for dififerent 
sized fans at varying pressure. 

The table should be made use of in the following 
manner : Having determined the quantity of air 
required for the entire building, we select from the 
table a fan which would give the proper capacity. 
In doing this three things must be considered. The 
fan must have sufficient capacity to deliver the 
amount of air recjuired. It must deliver this air 
with the minimum horsepower, and it must rotate 
with sufficient speed to produce a pressure in the 
fan system sufficient to overcome the resistance of 
the piping. It is always possible to select either a 
small fan driven at a high speed or a large fan 
driven at a low speed, both of which will deliver 
the same capacity of air. A large fan may be driven 
at so slow a speed that it will not produce sufficient 
pressure to overcome resistance of the air flues. 
Choose the largest fan that, driven at sufficient 
speed to overcome the resistance of the air flue, 
will deliver a proper quantity of air for the pur- 
pose of ventilation. As an example: Suppose we 
wish to deliver to a building 10,000 cubic feet of 
air per minute. Referring to the table, we see 
that we may use an 80-inch fan driven at 400 revo- 
lutions, in which case there would be 'required 5 
horespowers to drive the fan and the pressure pro- 
duced would be .713 ounce. Or we might use a 
120-inch fan driven at 125 revolutions per minute, 



Notes on Heating and V^entilation 2^9 

in which case the power required to ch'ive the fan 
would be 2.9 horsepowers and the pressure pro- 
duced would be .153. In the first case the fan is 
small and being driven at high speed the pressure 
produced is far more than necessary to overcome 
the resistance requiring an excessively large horse- 
power to drive it. In the case of the 120-inch fan, 
while the horsepower is much lower the pressure 
is insufficient to overcome the ordinary resistance. 
For ordinary purposes the pressure should be about 
.25. Referring again to the table, we see that the 
100-inch fan driven at 200 revolutions per minute 
would require 3.15 horsepow^ers and produce a 
pressure of .274. This would be about the proper 
size of fan to select. The pressure required to over- 
come the resistance of the building depends very 
largely upon the capacity and design of the flues 
and the resistance of these flues is largely a matter 
of judgment and experience. 

The determination of the proper quantity of heat- 
ing coil to raise the air to a given 
temperature will depend primarily Heating Coils. 
upon the amount of heat given ofif 
per square foot of heater coil. 

Table XXXV is obtained from the results of ex- 
periments made by the American Blower Company, 
of Detroit, and shows the condensation and heat 
given off by ordinary pipe heater coils under dif- 
ferent conditions. Knowing the heat given oflf 



Table XXXV 



Condensation and Heat Given Off by 
Heater Coils. 



a. 




<v 




<v 




T3 




C/) 


o 




^ 


o 


8 


C 


C/5 


cr 


0) 


c 


iX 


o 


Q. 


•4-* 




o 


O 


4> 

c/) 


^m 


, 


4> 


O 


B 


2 


3 




2 





8 
12 
16 
20 
24 
28 
32 



p. 



o 
o 



»i4 

B 

3 
2 



8 
12 
1« 
20 
24 
28 
32 



TEMPERATURE AIR ENTERING COIL 0^-10° 



Velocity of Air 

1000 feet per 

minute. 



o 
2 



Velocity of Air 

1250 feet per 

minute. 



Velocity of Air 

1500 feet per 
minute. 



Velocity of Air 

1700 feet per 

minute. 



c o 

o o 

— **- '71 
t/i I- c 
=» O 
^^ 

u. E 

a» 

a 



3 "^ 

—• b6 'y> 

C3 c ^ 

I- ._ 0) 

i» > u 

<u — ^ 

C3 



S ^ '^ 

^ « 3 

S 3 P 

C '^' c 

a 



U 



P o 

■^ M <U 

u E <i^ 

c ? ^ 



c o 

cd 0; ;^ 

'71 I- r 

c « ^ 

U 3 O 

C </) C 

O u — 



4J-5 

S > M 
c ? ^ 

C3 



C O 
O O c/, 

(/5 C 



2.E 2^ 

C3 



2.9 

1.78 

1.53 

1.31 

1.20 

1.10 

1.05 



74 
94 
114 
130 
143 
152 



2.37 

2.1 

1.86 

1.68 

1.54 

1.45 

1.40 



65 


2.56 


60 


2.72 


82 


2.32 


77 


2.45 


98 


2.09 


93 


2.25 


115 


1.88 


108 


2.05 


128 


1.77 


122 


1.92 


140 


1.70 


134 


1.85 


148 


1.65 


140 


1.77 



55 
73 
88 
103 
117 
129 
133 



TEMPERATURE AIR ENTERING COIL 40°-50^ 



Velocity of Air 

1000 feet per 

minute. 



Velocity of Air 

1250 feet per 

minute. 



Velocity of Air 

1500 feet per 

minute. 



\'eIocity of Air 

1700 feet per 

minute. 





__ 




_ 


^ 






18,, 


4) -^ 


S S 


Oi o 


C O 


a> o 


£ o 


h C 


.2 o y) 


C O 75 


u o 


O O tfl 


ensat 
uaref 
ound 


2.E e 


— ^ T3 

CO a» c 
'^ b 3 

c rt 5 
it 3 2 


mperatu 

leaving 

degrees 


n ^ c 

c ^ ^ 
5: 3 5 


>eratu 
uaref 
grees 


rt a* c 

5 3 ® 


T3 3- a 


c ? a7 


T3 CT Cl 


•3 era 


c CT± 


T3 O- "• 


5 '^' c 


E I' T3 


C 75 £. 


E Tj-a 


c t/» c 


O •_ .3 


f'^ u. 


O u .- 


•'** u. 


w a 


,<1> ;- 


o «-.= 


U^ 


H.- 


'J%. 


•"•JS 


^^ 


^J^ 



go 

3 ^ 

2.E e 

E <i> -D 



1.75 
1.50 
1.41 
1.37 
1.32 
1.26 
1.14 



91 


2.07 


84 


2.37 


80 


2.52 


107 


1.80 


100 


2.06 


95 


2.23 


119 


1.65 


112 


1.89 


107 


2.02 


133 


1.60 


125 


1.80 


121 


1.90 


143 


1.50 


137 


1.67 


135 


1.77 


150 


1.40 


145 


1.56 


142 


1.64 


158 


1.30 


152 


1.48 


148 


1.52 



78 
93 
105 
119 
133 
140 
147 



Notes on Heating and Ventilation 211 

by the coil per square foot, under given conditions, 
the number of square feet of coil surface necessary 
may be obtained in the following manner : ^Multiply 
the air to be passed per hour by the difference be- 
tween the temperature of the outside air and the tem- 
perature of the air after passing through the coil. 
^Multiply this product by .2375. Divide the re- 
sult obtained by 13.3, multiplied by the condensa- 
tion per square foot of surface per hour, multiplied 
by 966. Let C = condensation per square foot of 
coil ; A^ = volume of air in cubic feet passing per 
hour ; F = square feet heating surface coil should 
contain ; t --=^ temperature outside air ; t' = temper- 
ature of air after passing coil ; then 

P^ -^375V(t— t) 

"~ 13.3 X 966 c- 

In most cases the condensation in the tempering 
coils can be assumed at about 2 pounds per hour 
and in the heating coils about i^ pounds. In ex- 
treme cases condensation as high as 5 pounds per 
square foot per hour have been reported. 

After determining the number of scjuare feet of 
surface in the heater the heater must be so de- 
signed as to allow sufficient air area for the passage 
of air through the heater coils. The coils as ordi- 
narily arranged are shown in Fig. 58. Sufficient 
area should be allowed in these coils for the ve- 
locity of air passing. This should not exceed 1,200 
feet per minute., except where coils are very large. 



212 Notes on Heating and Ventilation 

Tempering coils should not be less than 12 pipes 
deep. If the heater coils are made very shallow the 
condensation in the coil is so rapid that in cold 
weather they will hammer. 

The heater coil consists of a cast iron base into 
which is screwed i-inch steam pipes jointed at the 
top by nipples and elbows. The cast iron base for 




Lin. 



Fii'ure 58. 



each section is provided with a steam ihlet and 
drip, both connected to the cast iron heater base. 
Alost bases are constructed for four rows of pipes. 
Table XXX\ I gives the principal dimensions of 
the American Blower Company's heaters with the 
size of fan regularly used. 

Within the last few years 
Cast Iron Heaters. cast iron indirect radiators 

suitable for use with fans 
have been placed on the market. Figure 59 shows 
a group of ten of these sections. They are easier 



Notes ox Heating and Ventilation 213 

to handle in erection and less liable to rnst. The 
standard sizes on the market are 41 and 6o§/8 
inches in length; both sizes are 9^4 inches deep 
and each section takes up a width of 5 inches. 
The 60-inch section contains 17 square feet per 
section and the 40-inch section 11^2 square feet. 
The sections are tapped 2^ inches and may be 





Table 


XXXVI- 


-Heater Dimensions. 




Lineal feet 










Size 


_,.Ac'ity 








Net 9 ii 


Reg- 


of fan. 


of 1-inch 




— Connections. 


space in 


ular 


Steel 


pipe. 




Steam. Drip. 


Bleeder. 


SCJ. ft. 


Disc. 


plate. 


200 




2" 


1" 


%" 


5.4 


30 


80 


300 




2" 


1" 


%" 


7.6 


36 


90 


400 




2" 


1 V4" 


%" 


10.7 


42 


100 


525 




2" 


1 Vj " 


\" 


14.3 


48 


110 


650 




O" 


IV," 


1" 


17.7 


54 


120 


825 




21/2 


1V2" 


1" 


22.2 


60 


140 


1.175 




2V- 


1 1/," 


1" 


31*. 


72 


160 


1.525 




3" ' 


2// 


IV4" 


40. 


84 


180 


2,025 




3" 


"2" 


ly^" 


52.5 


96 


200 



bushed to the proper size, depending on the num- 
ber of sections composing the radiator. Fig. 60 
shows a curve of the steam condensation for these 
radiators with varying depth of coil and different 
velocities of air. Figure 61 shows the tempera- 
ture to which the air would be heated in passing- 
through these coils with varying depth of coil and 
dififerent velocities of air. The last two cuts are 
from the results given bv the American Radiator 
Co. 



214 Notes on Heating and Ventilation 

The success of the fan system depends very 
largely upon the design of the flues. The best 

form of flue is round, the 
Ventilating Ducts. next best form is square, 

or, if rectangular,, as nearly 
square as possible. All turns and branches should 




Figure 59. 

be made with easy curves. The size of the flues 
is ordinarily determined by the velocity of the air 
passing in the flues. In main ducts of large size 
a velocity as high as 2,000 feet per minute or over 
may be used. In the branch ducts the velocitv 
should not exceed 1,000 to 1,500 feet. In flues 



Notes on Heating and Ventilation 



215 



Condensation Chart 

Incoming air, o° Fahrenheit. Steam pressure, 5 pounds 







05 






10 






15 






20 


IT. 




25 


Ti 






P 




30 


^ 











35 


c 




40 












45 


u 











50 


X 




55 






60 


ex 




65 


<u 






n1 




70 


<-^ 






u 










Vb 


W 




80 


bti 






^ 




85 


.4—1 






OS 
(U 




90 


X 




95 


t*- 









2 


00 


4-) 



9 


05 









u. 


2 


10 




2 


15 


ri 






3 


:^ 


20 


cr 






C/J 


2 


25 


u 






(y 


V 


30 


Cu 









2 


35 


.2 


2 


40 


rt 






(« 


V 


4S 


U 








2 


50 











;^ 


55 











2 


60 




2 65 




2. 70 




2. 75 




2 


80 

































n 














\ 














































\ 


ly 












































\ 


\. 






































\ 






s 


S, 






































\ 


s. 




\ 


\, 






































\ 


\, 




> 


\, 
































\ 






s 


s. 






\ 
































\ 


V 




V 


\, 






\ 
































\ 


s. 






\ 






\ 


























\ 






S 


\, 






\ 






\ 


\^ 
























\ 


V 




V 


^. 






\ 






\ 


s^ 
























\ 


S, 






k 






\ 


V 




s 


\, 


















\ 






V 


\, 






\ 






\ 


N, 




N 


^"i 


^ 
















N 


V 




N 


\. 






\ 






S 


\, 






^ 


O- 
















\ 


s. 






\ 






\ 


V 




^ 


\, 






~<v 












\ 






s 


\, 






\ 






\ 


s. 




% 


^< 






\ 












\ 


s. 




V 


\, 






\ 






\ 


s. 






\ 


'0^ 




\ 


S^ 










\ 


\, 






\ 






\ 


s. 




N 


\, 






^ 






N 


s. 










N 


N, 






\ 






\ 


\, 




N 


"^H 


^ 




\ 






\ 


s 










\ 


\, 






\ 






N 


\, 






^' 


'0 




\ 


s 




> 














\ 






\ 






S 


\, 






^ 






\ 


s. 


















\ 






\ 


s. 




S 


^1 


A. 




\ 






s 


s. 


















\ 






s 


s. 






^' 


'0. 




\ 


\ 




> 




















\ 


V 




s 


\, 






% 






\ 


s. 
























\ 


s 




V 


<;i 


^ 




\ 






\ 


s. 
























\ 


s. 






^ 


0. 




\ 


s 






























V 


\, 






^ 






s 


\, 
































^ 


ip. 




N 






V 


\, 
































•^ 


?* 




\ 


\^ 






































^ 


V 




S 


\, 






































\ 


S^ 




V 


\, 






































\ 


\, 












































V 


\, 














































:^ 



500 600 700 -800 900 1000 1100 1200 1300 1400 1500 
Velocity of Air Through Heater in Feet per Minute 



1024 

1072 
1121 
1170 
1219 
1267 
1316 
1365 
1414 
1462 
1511 
1560 
1608 
1657 
1706 
1755 
1804 
1852 
1901 
1950 
1999 
2047 
2096 
2145 
2194 
2242 
2291 
2340 
2389 
2437 
2486 
2535 
2584 
2632 
2681 
2730 



3 
O 



o 



3 

X 



o 
o 

3 
cr" 






Figure 60. 



216 



Notes on Heating and Ventilation 



leading to the individual rooms the velocity should 
be from 600 to 1,000 feet per minute, depending 
upon their size. Where the ducts are of small size 

Temperature Chart 

Initial air temperature, o° Fahrenheit. Steam pressure, 5 pounds 
220' 

210' 

200/ 

190/ 

180/ 

170/ 

.t 160/ 

^ 150/ 

° 140/ 



4> 

e 

t— • 

C 

5 
o 



""■^ 






t=j 




















1 1 










H^^M 








^^^ 














r: — 
















1 












1 — 


F=] 


^^ 


'^~ 










































— 


»s^ 




=^ 


"^ 


^•^ 





































^ 
^ 

^ 










psd 




p— 1 




^ 


--S 








- 


' 


=4; 

1 

— 


^ 
^ 

^ 


Ho, 





- 


- 


— 


=^ 


=^ 


r 




'-^ 


=^ 


- — \ 


•--^ 




—^ 




_— 




1 







p 


Hffl 






^ 



130" 
120° 
110° 

100° 

90° 

80.° 

70.° 

60.° 

50.° 

40° 

30.° 

20° 

10.° 

0° 

500. 600 7(X). 800. 900. 1000. 1100. 1200 1300. UOJ. 15iKJ. 

Velocity of Air Through Heater in Feet per Minute. 
Figure Gl. 

this velocity is often reduced to 400 feet per min- 
ute. The velocity at the registers should not exceed 
300 feet per minute except in very large registers 



Notes on Heating and Ventilation 217 

so located that the current of air entering the room 
will not strike the occupants of the room. In all 
ordinary buildings, if these proportions of air ve- 
locities are used the resistance of the system will 
be from two to three-tenths of an ounce pressure. 
In designing the ducts for a fan system short bends 
and tee branches should be avoided. The bends 
should be long and the branches made with Y's. 
The inside radius of the bend should be equal to 
the diameter of the pipe as a minimum and where 
conditions will permit, twice the diameter of the 
pipe. \Miere branches leave the main ducts it is 
a common practice to place a deflecting damper at 
the bend of the branch. This is merely a piece of 
galvanized iron attached to the point of the branch 
which may be adjusted and fastened so that each 
branch will take its proper supply of air. Dampers 
controlled by the attendants in the building should 
be as few as possible. The reductions in the size 
of a flue should be made gradually. The angle of 
the reduction should not exceed 30"^. Xo round 
pipes less than 6 inches in diameter are used, and 
if rectangular, less than 6x8. A common arrange- 
ment of ducts is to let them radiate from the fan in 
the form of a tree, with trunk and branches. This, 
however, makes the duct system very expensive 
and a system having large feeding mains similar to 
a system of steam piping is the one more used as it 
can be designed to give satisfactory results. An- 



218 



Notes on Heating and \^entilation 



other very satisfactory method of distribution is to 
force all the air from the fan into a large duct or 
chamber in which the air has a very low velocity. 



Table XXXVII— Pressure Losses. 

Air. — Loss of Pressure in Ounces per Square Inch per 100 

Feet of ripe of Varying Velocities and Varying 

Diameters of Pipes. 



Velocity of Af» 
Feet per 
Minute. 



DIAMETER OF PIPE IN INCHES. 



Loss OF PreSSI'RE IK Ov.NfES- 



600 
1,200 
1,800 
2.400 
8,000 
8,600 
4,200 
4,800 
6,000 



.400 


.200 


.133 


.100 


.0*0 


.067 


.057 


1.600 


.800 


.5:« 


.400 


.3-20 


.267 


.22? 


3.600 


1.800 


1.200 


.»00 


.720 


.600 


.514 


6.400 


3.200 


2.133 


1.600 


1.280 


1.067 


.914 


10.000 


5.000 


3.3.S3 


2.500 


2.000 


1.667 


1.429 


14.400 


7.200 


4.800 


3.600 


2.880 


2.400 


2.a57 




9.800 
12.800 


6..i.'>3 
8..133 


4.900 
6.400 


3.920 
5.120 


3.267 
4.267 


2.800 
8.657 






20.000 


13.333 


10.000 


8.000 


6.667 


6.714 





.050 

.200 

.450 

.800 

1.2^ 

1.800 

2.4.50 

3 200 

5.000 



Velocity of Air 
Feet per 
Minute. 



DIAMETER OF PIPE IN INCHES 



10 



11 



12 



14 



16 



18 



Loss OF Pressure i.n Olnces. 



20 



600 
1,200 
1.800 
2,400 
3,000 
8.600 
4.200 
4.800 
6,000 



.044 


.040 


.036 


.033 


.029 


.026 


.022 


178 


.160 


.145 


.133 


.114 


.100 


.089 


400 


.360 


.327 


.300 


.257 


.225 


200 


.711 


.640 


..582 


..533 


.457 


.400 


356 


1.111 

1.600 


l.OQO 
1.4^6 


.909 
1.309 


.833 
1.200 




"".*900 


"".'800 


1.029 


2.178 


1.960 


1.782 


4.633 


1.400 


1.225 


1.089 


2.844 


2.560 


2.327 


2.133 


1.829 


1.600 


1.422 


4444 


4.000 


3.636 


3.333 


2.857 


2.50e 


2.222 



.020 
OSD 
ISO 
.320 



.720 

.980 

1.280 

2000 



Velocitj- of Air 
Feet per 
Minute. 



DIA.METER OF PIPE IN INCHES. 



22 



24 



28 



32 



36 40 



44 



Loss of Pre.v^uke i.n Olnces. 



48 



600 
1,200 
1,800 
2,400 
8,600 
4,200 
4,800 
6,000 



.018 


.017 


.014 


.012 


Oil 


.010 


.009 


.073 


.067 


.057 


.050 


.044 


.040 


.036 


.164 


.156 


.129 


.112 


.100 


.090 


.082 


.'291 


.267 


.239 


.200 


.178 


.160 


.145 


.6.55 


.600 


.514 


.4.50 


.400 


.360 


.327 


.891 


.817 


.700 


.612 


.544 


.490 


.445 


1.164 


1.067 


.914 


.800 


.71J 


.640 


.582 


1.818 


1.667 


1.429 


1.250 


i.m 


1.000 


.909 



.008 

.ats 

.075 

.i:« 
.300 
.408 
.583 

.883 



Notes on Heating and Ventilation 219 

The rooms take their air from this chamber by 
means of vertical flues controhed by proper dam- 
pers. These large chambers are called Plenum 
chambers. A good example of this is shown in the 
construction of the new Engineering building. Uni- 
versity of ?^Iichigan. In this building the corridor 
on the ground floor has a false ceiling about 3 feet 
below the second story floor. This leaves a space 3 
feet high by 12 feet wide extending through the 
entire building. Into this space two separate fans 




Figure 62. 



deliver their air. The space acts as a Plenum 
chamber and the individual flues leaving the rooms 
take their air from this Plenum chamber through 
volume dampers which may be set and fastened 
after the proper position has once been determined. 

Table XXX\^II shows the loss of pressure per 
I GO feet of pipe for varying velocities and varying 
diameters of pipes. This table is quite liberal and 
allows for two ordinary 90° bends per 100 feet. 

Where the building is heated entirely by a fan 



220 Notes ox Heating and Ventilation 

system it is necessary to devise some arrangement 

by which the room may be 

Air Mixing Systems. furnished with hot air or 

tempered air. In case the 
room becomes too warm, to close ofif the hot air 
register would do away entirely with ventilation 
and it is necessary to provide some means of intro- 
ducing tempered air. The method usually used is 
shown in Fig. 58. Wdiere each room is connected 
both to the warm air chamber and to the cold air 
passage, the dampers being connected so that when 
the warm air is turned ofif cold air is introduced 
into the room, or vice versa. In this case the mix- 
ing damper is located near the fan and preferably 
controlled automatically. Another system shown 
in Fig. 62 has entirely separate cold and hot air 
flues which are led to the base of vertical flues lead- 
ing to the rooms, at which point there is introduced 
a mixing damper similar to the mixing damper 
shown in Fig. 58. 

The flues for fan systems are ordinarily con- 
structed of galvanized iron with double lap joints 

riveted and soldered. The 
Materials of Flues. ducts should be made as 

nearly as possible air-tight. 
The weight of material used for ducts depends 
upon the size of the duct. It ordinarily varies from 
Xo. 26 to Xo. 16 gauge. Large ducts are also 
made of sheet iron with close riveting. When 



Notes on Heating and Ventilation 221 

ducts are made of sheet iron the ducts are painted 
and then asphalted. Where it is necessary to build 
ducts underground they are built of brick or ce- 
ment. The cement, if anything, is preferable to 
brick, as it does not absorb odors as easily and may 
be plastered to make a smooth job. Where pos- 
sible it is desirable to build the ducts and flues into 
the building itself, making them of permanent ma- 
terial. Brick or cement ducts built into the build- 
ing and so arranged that they may be examined and 
cleaned easily are the most satisfactory. Wood is 
always a bad material to use for ducts and should 
be avoided. Where it is used the ducts are lined 
with tin, owing to the fact that wood usually 
shrinks, leaving open joints. 

\^ent ducts from closets should be carried out of 
the buildings separately from the other vent flues. 
Where these ducts are made of brick they should 
be lined with galvanized iron to prevent the odors 
from the closet being absorbed by the brick. It 
is very desirable that closet vents should be col- 
lected at convenient points and then exhausted from 
the building by means of a fan. This prevents 
the odors from the toilet rooms being carried back 
into the building. 

Disc fans are used where the resistance to be 
overcome is very slight or in cases where the ducts 



222 Notes on Heating and Ventilation 



Table XXXVIII— Disc Fan Efficiency. 

Disc Ventilating Fan — Capacities, Speeds and Horse Pow- 
ers. (American Blower Co.) 



Are Veloc- 
ity IN Ft. 

PBR MlN. 


Size 
Fan 


18 


21 


24 


30 


36 


42 


48 


54 


60 


72 


84 


96 


itiS 


126 


600 


Free 


Cu. Ft. 

R. P. M. 

H. P. 


1&60 
327 
.016 


1440 
280 
.022 


1880 
245 
.028 


2940 
196 
04a 


4230 

165 

• 064 


5772 
140 
087 


7536 
122 

"3 


9540 
110 
143 


1 1 770 

98 

•177 


16960 

82 

253 


23090 

70 

• 345 


.450 


38160 

55 
573 


47160 

so 
706 




Heater 


R. P. M. 
.H. P. 


530 
•053 


453 
072 


.094 


3»7 
•'47 


267 
.212 


227 
.288 


'97 

•377 


178 

■ 477 


158 
•59° 


.849 


ir3 
> 15 


100 

'•51 


89 
1. 91 


81 
2.3s 


700 


Free 


Cu. Ft. 

R. P. M. 

H. P. 


'235 
370 
.025 


1680 
328 
■035' 


2200 
280 
.045 


3400 
230 
.070 


494° 
190 
.110 


6730 
J 64 
•'36 


8800 
145 
.178 


11120 

127 
.227 


43750 
1 12 

.279 


19760 

96 

.402 


26950 

82 

.548 


35016 

72 

.740 


44500 
■ 62 
• 905 


55000 

58 

I. It 


Heater 


R. P. M. 
H. P. 


600 
,071 


53° 
■ .096 


458 
.126 


.196 


307 
.283 


266 
.384 


234 
■5°3 


206 
.636 


i78 

.786 


158 
I 13 


132 
'•54 


n6 
a. 10 


JOO 

2.52 


92 

3 14 


800 


Free 


Cu. Ft. 

R. P. M. 

H. P. 


1410 

435 
.036 


1920 
373 
048 


2510 
326 
,068 


3820 
262 
098 


5650 
218 
.142 


7700 
187 
.192 


10300 
164 
•25' 


12710 
145 

• 3'7 


15710 
'3' 
•392 


22600 
no 
.562 


30400 

94 

,766 


40150 

83 
1.00 


50900 

73 
I 27 


62800 

66 

'•57 




Heater 


R. P. M. 
H. P. 


705 
.106 


604 
149 


527 
..89 


424 
»94 


353 
.426 


302 
.579 


265 
.756 


234 

■957 


212 
1.18 


'78 
'7' 


152 
2.32 


134 

3 20 


118 
3^83 


107 

4 73 


900 


Free 


Cu. Ft 

R. P. M. 

H. P. 


1584 

490 

• 048 


2160 
425 
06s 


2826 
36S 
.085 


4410 
285 
'32 


6354 
246 
.190 


8650 
210 
•258 


11304 
184 

.338 


14310 
164 
.42b 


17667 
146 
•53° 


25443 
.762 


34642 

106 

1.04 


45234 
. 93 
I 35 


57250 

82 

1.72 


70650 
74 

2.12 




Heater 


R.P. M. 
H. P. 


792 
•143 


770 
•195 

2400 

470 
.080 


595 

254 


461 

3" 7 


398 

• 572 


340 
.780 


298 
1 .02 


265 
1 .29 


236 
J 59 


199 
2.29 


'73 

3 '2 


150 

4.07 


132 

S15 


119 
6.36 


1000 


Free 


Cu. Ft. 

R. P. M. 

H. P. 


1770 
545 
057 


3HO 
406 
.104 


4900 
328 
142 


7060 
275 
■233 


9610 

234 
•3'7 


12560 
205 
■4'3 


159C0 
181 
.520 


19630 
166 

■647 


28270 
136 
•933 


38480 

120 

1.27 


50265 

103 

1.66 


63600 

9' 
2.09 


78540 

82 

2.56 




Heater 


R. P. M. 
H. P. 


883 
.204 


760 
.276 


657 
362 


53° 
.565 


445 
.814 


378 
I II 


332 
1 45 


.293 
'•83 


2C8 

2 .26 


220 
3 26 

33900 

164 

1.62 


194 
4 44 


167 
577 


.147 
7 33 


■ 132 

9 OS 


1200 


Free 


Cu.Ft. 

R. P. M. 

H. P. 


2112 

654 

. lOI 


2880^ 
560 
.138 


..3768- 
490 
.180 


5880 
398 
.280 


8472 

33° 

.■405 


"54' 
280 
■ 550 


15072 
245 
.716 


19100 
218 
.910 


23566 
I96 
'•'3 


46176 

140 

2.20 


60312 

124 

287 


76300 
110 
3^63 


94240 
4.4S 




Heater 


R. P. M. 
H. P. 


1059 
.300 


912 

.409 


.,788 
534 


636 
•832 


534 
1 .20 


1.64 


.396 
2.14 


351 

2.70 


322 
3 37 


264 
4.85 


234 
6.60 


200 
8.63 


176 
10.8 


.160 
'13 3 


1400 


Free 


Cu. Ft. 

R. P. M. 

H. P. 


2475 
767 
•»33 


3360 

655 
.180 


4400 

570 
•235 


6850 
460 
.368 


9870 
388 
•53° 


1347° 
327 
721 


17600 

286 
.942 


22270 
254 
' '9 


27500 
230 
'•55 


39600 

190 

2.12 


53900 

164 

•2.89 


70300 

144 

, 3 77 


88950 

128 

4 77 


109500 
5.89 




Heater 


R. P. M. 
H. P. 


1235 
.487 


1064 
.660 


919 
.864 


742 

'■35 


623 
195 


52S 
2.64 


463 

3 46 


410 
4.38 


376 
5 4° 


308 

,7-88 


•' 274 
10.6 


234 
'18 


205 
'75 


184 
21 .6 


1600 


Free 


Cu. Ft. 

R. P. M. 

H. P. 


2830 
875 
.'85 


3850 
750 
252 


5000 
656 
.330 


7810 
526 
•5'5 


1 1300 
438 
•742 


15400 

375 
1 .01 


20050 
332 
'■34 


25400 
298 
1.67 


3.400 
264 
2 .06 


45200 

220 

'2.97 


61500 

1 88 

4.05 


80000 

16s 

5.28 


101200 

.46 

6.68 


125200 
8.25 




Heater 


R. P. M. 
H. P. 


1412 

•735 


1216 
1 .00 


1050 
'3.' 


848 
2 04 


712 

2.94 


603 
4.00 


537 
5 23 


468 
6.62 


429 
8.17 


352 
II. 8 


314 
16.0 


• 268 
20.9 


26.5 


210 

■32 ■ 7 


1800 


Free 


Cu. Ft. 

R. P.M. 

H. P. 


3170 
980 
.247 


4320 
840 
336 


5630 
732 
• 440 


8850 

69° 
.686 


12700 

490 

.-•99' 


17300 
420 
'•35 


22600 
368 
1.76 


28600 
330 

2.22 


35200 

294 

2.75 


51000 
245 

396 
16.9 


69000 

210 

J 39 

354 
23.0 


90200 
'85 

•302 
30.0 


114000 


141000 

148 

»i.o 




Heater 


r:p:m. 

H. P. 


T588 
'OS 


1368 
« 43 


1181 
1.87 


954 
2 93 


801 
4 ■23 


679 
5 75 


595 
7.50 


526 
9.50 


"483 
11.7 


263 
38.0 


236 

47 


2000 


Free 


Cu. Ft. 

R. P. M. 

H. P. 


3520 
1090 
336 


4800 
935 
.456 


6280 
815 
•597 


9800 
655 
93' 


14126 
545 

'•34 


19^40 
47° 
.83 


a5'2o 
410 

2 39 


31800 
363 

3 02 


39260 

327 

3 73 


56510 
272 
5 38 


76960 
234 
7 3' 


100520 

206 

9 55 


127200 
182 
12. 1 


157100 
164 
'4 9 




Heater 


R. P. M. 
H. P. 


1764 
1.30 


1520 
'77 


1312 
2.30 


1060 
3.60 


890 
5 '5 


755 
7.05 


664 
9 25 


585 
11.7 


528 
'4 5 


440 

20,8 


380 
28. s 


336 
37 


292 
46.8 


262 
578 


2200 


Free 


Cu. Ft. 

R. P M. 

H P. 


3890 
1200 
424 


4300 
1050 
.576 


6800 
900 
■754 


10800 
720 
I. 18 


15520 
600 
1.70 


21130 

5'5 

23' 


27600 

450 

.3 02 


35000 
400 
3 82 


•43200 

360 

4 72 


62200 

300 

6.79 


84700 

257 

925 


I 10500 

228 

12 I 


139800 
202 
15 3 


172500 

'75 

18.8 




^ Heater 


R P.M. 
H. P. 


1940 
17" 


r 1700 

2 30 


1460 

3.00 


1163 
4-70 


97' 
6 80 


830 
9 25 


727 
121 


645 
'5 3 


582 
18 8 


485 

27.0 


4'5 

37 


368 
48 2 


323 
61 .0 


284 
82 



Notes on Heating and Ventilation 223 

are very large, with easy 
turns and of very short Disc Fans, 

length. They are exten- 
sively used for exhausting the air from the vent 
flues and where the vent flues are short and large 
they give good satisfaction. The capacity, speed 
and horsepower of various sizes of disc fans is 
shown in Table XXXVUI. 

Example. — As an example of the fan system 
consider an auditorium. The dimensions of the 
room are 40 feet g inches by 79 feet 6 inches by 
127 feet 9 inches. The volume of the room is 413,- 
000 cubic feet. It has 203 square feet of glass sur- 
face and 5,441 square feet of wall surface. The 
heat lost from the room, figuring in the same way 
as we have for previous examples, will be 168,010 
B. T. U's. The hall has a seating capacity of 
2,500 persons. Allowing 2,000 cubic feet of air 
per person, the necessary air to be admitted to the 
room will be 5,000,000 cubic feet of air per hour. 
This equals 383,000 pounds. In order to heat the 
room with this quantity of air entering, it will be 
necessary to heat the air but 1.85 degrees so that 
the air admitted to the room for ventilating pur- 
poses will be far more than that necessary for heat- 
ing purposes. It is best, then, to figure on admit- 
ting air only for purposes of ventilation. To heat 
this air from zero to 70° would require 383,oooX 
.2375X70=6,353,000 B. T. U's. Referring to 



224 Notes on Heating and Ventilation 

Table XXXV^ we see that a heater coil 12 pipes 
deep will heat air having a velocity of 1,250 feet 
per minute to a temperature of 82°, which is prob- 
ably about the proper assumption to make in this 
case. The coil will condense 2.1 pounds of steam 
per square foot per hour. Each pound gives up 
about 970 heat units, so that each square foot of 
heater coil will give ofif about 2,000 B. T. U's. per 
hour. Then the number of square feet of heater 
coil required would be 6,350,000 -:-2,ooo^=3, 175 
square feet. The heater coils are usually made of 
I -inch pipe and each square foot of surface is 
equivalent to about 3 feet of i-inch heater pipe, 
hence there will be required 3,175X3 or 9,525 feet 
of I -inch pipe in the heater coils. The air to be 
admitted to the hall is 5,000,000 cubic feet per 
hour or 83,300 cubic feet per minute. The usual 
velocity allowed for the air passing through the 
heater coil is 1,200 feet per minute. This will re- 
quire an air area in the heater coil of 83, 300 -^^ 1,200 
=69.5 square feet. The area in the various heater 
coils will be found in the blower company's cata- 
logues and is also given in Table XXXAT. This 
will determine the size of the heater coil to be 
used. 

On account of the size of the hall and the 
amount of air introduced, it will be best to have 
two fans for delivering air into the building. Each 
fan would then need a capacity of 41,650 cubic feet 



Notes on Heating and Ventilation 225 

per minute. In order to overcome the resistance 
of the flues the pressure should be from .2 to .3 
of an ounce at least. From the table of fan capaci- 
ties we see that a 180-inch fan running at 150 rev- 
olutions would require 19.6 horsepowers and pro- 
duce a pressure of .503 ounces. This, how-ever, 
is ^ higher pressure than would be desired unless 
the flues were very long and had a number of 
curves. If the flues are short and straight we 
could use two 200-inch fans running at 100 revo- 
lutions. These fans would deliver 55,000 cubic feet 
of air each, with a pressure of .273 ounces and re- 
quire 12.9 horsepower to drive them. By using a 
larger size of fan 6.7 horsepow^ers (for each one 
of the fans) would be saved. Assuming the air to 
be delivered to the hall by four ducts, these ducts 
being large, it would be reasonable to allow a 
velocity of 1,500 feet per minute in the duct. Each 
duct would have to carry 20,800 cubic feet of air 
per minute ; 20,800-^1,500=13.8 square feet in area. 
As the registers of these ducts wnll be large and 
situated well above the head line, it would be safe 
to allow^ a velocity of 400 feet per minute to the 
register. The area of each register, assuming that 
there are four entering the room, w^ould be 26 
square feet. The vent flues leaving the room should 
have an area about equal to the hot air flues. 



CHAPTER XII , 



A CENTRAL HEATING SYSTEM. 

It is not intended in this chapter to discuss the 
design of heating systems, such as is used in the 

heating of a city, but sys- 

Design and Location, terns that are in use for the 

heating of pubhc institu- 
tions, or groups of buildings. The type of system 
to be used in a given installation depends very 
largely upon the location and character of the build- 
ings to be heated. No two systems, even though 
designed by the same engineer, will be the same, 
and the suggestions made in this chapter can be 
but general. 

Before starting the design of a central heating 
system it is first necessary to have a careful survey 
of the property. This survey should show the ex- 
act location of the buildings to be heated, the ele- 
vation of the basement and first floor, together with 
a general profile of the ground through which the 
tunnels or pipes are to be run. The profile of the 
ground will largely decide the proper location of the 
power house. The power house should be located 
as nearly as possible to the buildings to be heated 
or as near as possible to the largest steam load. It 



Notes on Heating and Ventilation 227 

should be low enough, if the profile of the land will 
permit, so that the condensation of the return mains 
may be returned to the power house by gravity. 
If possible, it should be so located that the floor of 
the boiler room may be drained to the sewer. Con- 
siderable difficulty is usually experienced to carry 
away the water, which results from the cleaning and 
blowing ofif of the boilers if no sewer connection 
can be made. The question of the soil, the location 
of the railroad siding, the water supply and the 
general appearance of the power house must also be 
taken into consideration. 

Before designing the power house the type and 
general form of boilers must be determined. If the 
power house is to work on a low pressure system 
with a pressure under lOO 
pounds, either fire or water Bailers, 

tube boilers may be used. 

In general, for this service fire tube boilers are very 
satisfactory, as they have large water storage, re- 
pairs are easily made, and the boiler may be 
crowded considerably beyond its rating. The 
economy of water tube and fire tube boilers is prac- 
tically the same. 

The principal objection to fire tube boilers, ex- 
cept of the Scotch marine type, is the large space 
which it occupies. If the power house is to be op- 
erated on high pressure, that is, over lOO or 125 
pounds, then only water tube or Scotch marine boil- 



228 Notes on Heating and Ventilation 

ers can be used. The size of the boiler must be deter- 
mined by the amount of steam which is to be used 
l)y the radiation and other devices taking steam 
from the boilers. The steam used bv the different 
forms of radiation can be determined by reference 
to the radiator tables previously given. Aftei 
having once determined the cjuantity of steam the 
plant is expected to use, it is customary to assume 
that each scjuare foot of heating surface in a boiler 
will evaporate about three pounds of water. This 
determines the total amount of heating surface that 
the boilers should contain. The boiler units should 
be so selected that one boiler or one set of boilers 
will take care of the plant during the light load 
period of operation, that two boilers or sets of 
boilers w411 take care of the average operating load. 
In addition to this there should be a boiler or set 
of boilers that will take care of the maximum con- 
ditions of load. There should always be a sufficient 
number of boilers in the plant so that at least one 
boiler or set of boilers can be out of service for a 
considerable period of time for cleaning or repair- 
ing. In a central heating plant using the gravity 
return system, it is necessary that all boilers have 

their water line at the same level. 

Systems of Distribution. 

The general design of a piping system and its lo- 
cation will depend upon the system of distribution 
adopted. 



Notes on Heating and Ventilation 229 

If the gravity return system is used no main feed 
pump is necessary, the water returning by gravity 
to the boiler, as previously 
described. AVith this sys- Oravity System, 

tem any difference in pres- 
sure between that in the boiler and that at the ex- 
treme point in the piping system will result in a 
corresponding elevation of the water level in the 
return system at the extreme point — each one pound 
drop of pressure in the steam piping corresponds 
to an increase in the level of the water in the return 
piping of 2.30 feet. It is essential, then, that the 
gravity return system with a difference in pressure 
between that at the boiler and that at the extreme 
point of the piping system be comparatively small. 

The difference of pressure assumed wall deter- 
mine the size of the piping. In gravity systems it 
is usual to allow for the drop of pressure not over 
two pounds between the boiler and the extreme end 
of the system. 

In some cases the gravity return system has been 
used over quite an extended area, the most distant 
building heated being as far as 2,500 feet from the 
boiler, and the system has given very good satis- 
faction. 

In a central heating plant using the gravity re- 
turn system unless the steam mains are six to eight 
feet above the return it is necessary that the steam 
condensed in the mains be dripped separately from 



230 Notes on Heating and Ventilation 

the main returns in the building and this drip 
pumped back to the boilers, preferably by a pump 
and receiver, or some other mechanical means, such 
as a return trap. This pump and receiver should be 
of sufficient size to take care of the steam condensed 
in the mains when the steam is being turned on and 
the condensation is excessive. By returning the 
condensation of the mains separately, excessive 
hammering is avoided and the system can be started 
much more rapidly. Gravity return is used only 
where the boiler pressure does not exceed ten 
pounds. 

The high pressure heating system is being little 
used for general heating purposes. It has some 
advantages. The pipes are smaller and radiation is 

more effective per square 
High Pressure System, foot. The disadvantages, 

however, outweigh the ad- 
vantages in most cases. In the high pressure sys- 
tem cast iron radiators are not safe, as they are not 
usually made to operate at a pressure to exceed 
twenty pounds. The pipe coil or other form of 
radiation must be used. The cost of producing 
steam, the chance of accident, and the cost of re- 
pairs are increased. It is not possible to use ex- 
haust steam with a high pressure system. When 
pipe coil radiation is used it would be safe to carry 
a pressure up to lOO pounds. In determining the 



Notes on Heating and Ventilation 231 

size of steam mains for such a system a loss of 
pressure as high as ten pounds would not be con- 
sidered excessive. In the high pressure system each 
building usually sends its condensation back to the 
return system through a trap so that the pressure on 
the return is only slightly above the atmosphere. 
This condensation returns to a surge tank, from 
which the feed pumps return it back to the boilers. 
The drip from the steam mains is dripped directly 
back into the return system. 

In a very large system where it is difficult to get 
enough difiference in elevation between steam and 
return mains, or where the 

drop in pressure exceeds Low Pressure Pump 
two pounds, it is usual to Return System, 

install some form of pump 

return. One of the most common forms of pump 
return is to trap the return condensation of each 
building into the return main, which carries the re- 
turn back to a surge tank in the boiler room. From 
this surge tank the water is returned to the boiler 
by means of a pump. The drip from the steam 
main is trapped directly to the return main. The 
most objectionable feature of this system is the 
constant attendance and the repairs necessary to 
take care of the traps. 

In most cases the heating system is combined 
with some form of power system. This makes a 



232 



Noxks ON Hh:ating and Ventilation 



very economical coinbiiia- 

Combination of Power tion, as the exhaust from 

and Heating System. the power plant may be 

used in the heating system. 
Where the exhaust can be entirely utilized for from 
six to eight months of the year it is seldom profit- 
able to use condensing engines. 




Figure 63. 

There are two general schemes used for com- 
bining a power and heating system. In the simplest 
form the boilers are operated at a high pressure. 
The steam goes from the boilers to the engine, and 
after the steam leaves the engine it passes directly 
to the heating system. A by-pass pipe is carried 



XoTEs OX Heating and Ventilation 233 

from the high pressure steam main to tlie heating 
main and in this by-pass is located a reducing pres- 
sure valve. If for any reason the engine does not 
supply sufficient steam to maintain pressure on the 
heating system, then the reducing valve opens and 




Fisure 64. 



introduces live steam. The returns from the heat- 
ing system are carried back to the boiler by means 
of a pump. 

Fig. 63 shows the general arrangement of sys- 
tems of this kind with a by-pass for furnishing live 
steam to a heating system. This system depends 
in a measure for its success upon the action of the 
reducing pressure valve. 

The cross-section of a reducing pressure valve is 
shown in Fig. 64. Such valves have been found to 



234 



Notes on Heating and Ventilation 



be quite reliable when well designed and well made. 
The principal cause for trouble is when the valve 
becomes foul with dirt. In- a system of this kind 
the engine exhaust is always provided with a back 
pressure valve connected to the atmosphere. This 
valve is so arranged that if for any reason excessive 
pressure should accumulate in the heating system 



« 



iat^ P'-est u^t< QQ'^r'-s 



0:&^i 



9 a I if 




Figure G5. 

the valve would open and exhaust the steam into the 
atmosphere. The arrangement show^n in Fig. 63 
is most used in small plants and both the heat and 
the power can be taken from one boiler. In larger 
plants the heating boilers are operated on the low 
pressure and the power boilers on the high pressure 
system. In the high pressure system steam goes 



Notes on Heating and Ventilation 



285 



to the engine and pumps and is exhausted through 
an oil separator into the low pressure system. The 
pressure of the exhaust is determined by the pres- 
sure carried on the low pressure system. This sys- 
tem is particularly desirable where the heating load 
is considerably larger than the power load ; and 
where at times the engines are entirely shut down 
and only the low pressure system is operated. Fig. 
65 shows a sketch of this arrangement. 




£'/euc://'/<in 



P/< 



Figure 66. 



Method of Carrying 
Pipes. 



In carrying pipes from one building to another it 
is always desirable, if possible, to carry them under- 
ground. Carrying under- 
oTOund affords much bet- 
ter heat insulation, the 
pipes are more easily sup- 
ported and are less apt to be disturbed. The 
simplest method of underground distribution and 
the cheapest is to enclose the pipes in a pine board 
case, as shown in Fig. 66. This arrangement, how- 
ever, is not as desirable as a tunnel system, the heat 
insulation is not as satisfactory and the pipes are 



23() Notes on Heating and Ventilation 

more difficult to get at for repairs. Its chief rec- 
ommendation is that it is cheap. In most cases it 
should be used for work where the expense of a 
tunnel system would not be warranted. 

A system quite largely used is to enclose pipes in 
pump logs, that is, hollow wooden pipes. These 
pipes are creosoted and filled with an asphalt paint 
or some other means of preservation. They are 
often lined with tin or some other form of metal 
lining. The pipe is passed through the pump log 
and is usually covered with about one inch of some 
standard form of pipe covering. This method of 
running the pipes furnishes quite satisfactory heat 
insulation. It is much more durable than the pine 
board duct, it is easier to install and easier to re- 
place in case of repairs. It has, however, the dis- 
advantage of making the pipe quite inaccessible ancj 
in case of accident the removal of the entire system 
is necessary; this in many places is very expensive. 
The builders of one of these pipe ducts stated that 
the loss in the pipes enclosed in this manner is from 
one-fourth of one per cent to six per cent per mile 
of pipe delivering steam at its full capacity. The 
larger the pipe the smaller the proportional heat 
loss. Fig. 67 shows a cross section of a pipe log 
with covering. This pipe log construction is most 
used in central heating systems for building con- 
nections and where only one pipe is to be used in 
supplying the building. 



Notes on Heating and Ventilation 237 



Where it is necessary to run a number of pipes 
the most desirable method is to run through tunnels 
made of brick or cement. The size and form of 
tunnel used will depend upon the number of pipes 
to be carried, the character of the soil and the 
depth into the ground. Where tunnel systems 
have been installed the general experience has been 
that they more than paid for themselves in a short 
time, as they entirely do away with the necessity of 
taking up the pipe and allow for repairs and fre- 

Tin /./nm^ 





^/ev^i/'/cn 



PA 



on 



Figure 67. 



quent inspection. Fig. 68 shows a small sized tun- 
nel. This tunnel has been used for carrying pipes 
not over 8 inches in diameter. The tunnel is 3 feet 
6 inches wide, 4 feet 6 inches high. It is made of 
brick 4 inches thick, with i inch of Portland cement 
outside. This cement is painted a thick coat of 
tar or asphalt to below the crown of the arch. 
Wherever the supports come the tunnel is ribbed 
with an 8-inch rib of brick 16 inches wide. This 
rib is placed about every 10 feet. A tunnel of this 



238 Notes on Heating and Ventilation 

kind has been in use for some time and has given 
good satisfaction. It is not desirable to use this 
sort of tunnel for large pipe or where the tunnels 
are to be frequently inspected. 




Figure 68. 



For larger pipes the section shown in Fig. 69 is 
much more desirable. This tunnel is 5 feet by 6 feet 
inside dimensions. The tunnel is made of two 
courses of brick or about 9 inches thick. It is plas- 



Notes on Heating and Ventilation 



239 



tered on the outside with i inch of cement and 
then tarred down to the crown of the arch. At the 



r^o^ 




Figure 69. 



lowest point of the tunnel on each side is shown a 
3-inch tile, which serves to carry away the drainage 
around the tunnel. If possible, this 3-inch tile 



240 Notes on Heating and Ventilation 

should be brought to some drain. In moist clay 
soils it is sometimes found necessary to run a tile 
under the middle of the tunnel connecting with the 
inside of the tunnel so that seepage through the 
tunnel walls may be carried off either to the sewer 
or to the pumping plant. In sand and in gravel soils 
this is not necessary, as almost no difficulty would 
be experienced from leakage. Fig 70 shows a tun- 
nel made for carrying two large pipes. The tunnel 
is 5 feet 6 inches by 6 feet 6 inches and gives ample 
passageway between the pipe supports for easy 
access at all times. 

The cost of tunnels depends upon the nature of' 
the excavation and the price of materials. To give 
an approximate idea of what tunnels cost, the tunnel 
shown in Fig. 68 has been constructed, including 
excavation, back filling and all necessary material 
for $4 per linear foot. The tunnel shown in Fig. 
69 has been constructed for S6 per linear foot, and 
the tunnel shown in Fig. 70 has been constructed 

for $6.50 per linear foot. 

The size of the pipe necessary to carry a given 

quantity of steam is determined by the allowable loss 

of pressure that the sys- 
Sizes of Pipes. tern will permit. In a low 

pressure system this loss 

of pressure should not exceed 2 pounds. In a 

high pressure system it should not exceed 10 



Notes on Heating and Ventilation 



241 



pounds. The rule most commonly used is called 
Babcock's rule, and is as follows : 
Let W=weight of steam in pounds flowing per 
minute. 




Figure 70. 



w=the weight of a cubic foot of steam. 
p^=::^pressure in pounds per square inch of steam 
entering pipe. 



242 Notes on Heating and Ventilation 

p2=pressure in pounds per square inch of steam 
leaving the pipe. 

d=diameter in inches. 

L^length of pipe in feet. 



Then \V=87 ^ P (P'-P^)^' 

The best way of handUng this expression is to 
assume different diameters of pipe and then try a 
number of standard pipe sizes. In this way deter- 
mine the pipe size which approximates most closely 
the weight of steam which it is desired to carry. 

In low pressure gravity return systems the return 
is usually taken as one-half the pipe size of the 
steam main up to lo inches. Above lo inches the 
size is taken as one-half the size of the steam main 
minus one size. As, for example, a lo-inch main 
would require 5-inch return, a 14-inch would re- 
quire a 6-inch return. The size of drip main for a 
given steam main depends entirely upon the length 
of the main. It should never be less than ^-inch 
and it is seldom necessary to make the pipe over 
i]4-inch. A ij4-hich drip main will take care of 
2,000 feet of 12-inch pipe, providing the pipe is well 
covered with standard covering. 

When pipes are carried through tunnels it is 
necessary to provide a different form of hanger than 



Notes on Heating and Ventilation 243 

in building work. In tun- 
nel work the head room is Hangers and Anchors. 
so limited it is ordinarily 

impossible to suspend pipes from above and they 
must have some form of roller hanger. Fig 70 
shows ball-bearing hangers for 12-inch pipe and 
roller hangers for the 6-inch pipe. Fig. 68 shows a 
very simple form of roller hanger. Fig. 69 also 
shows a form of ball-bearing hanger for 8-inch 
pipe and roller bearing for 4-inch pipe. The ball- 
bearing hangers shown in these figures have given 
very satisfactory results. They are expensive, but 
the expense is warranted. In tunnel work the clear- 
ance is so small that it is necessary to know exactly 
where the expansion is to be taken up. The only 
way to be certain of this is to anchor the pipe at the 
point desired. These anchors are usually made of 
heavy cast iron with wrought iron straps enclosing 
the pipe. The hangers should be built into the 
tunnel or building walls and should pass entirely 
through the wall, projecting 4 inches or more on 
the opposite side of the wall. The anchors should 
not be built into walls that are less than 12 inches 
thick, and preferably they should be 16 inches thick. 
In putting in hangers and supports in tunnel work 
it is a very important thing to see that a clear space 
is left through the center of the tunnel which will 
give easy access to the tunnel. The easier the access 
and the more comfortable the tunnel for passage, 



244 Notes on Heating and Ventilation 



the more frequent will be the inspections, and such 
inspections insure of the piping being kept in the 
best possible condition. 




Figure 71. 



OUTLET ^' PIPE 

Air valve for use on steam mains with Paul 
valve. 



Fig. 71 shows an air valve adapted for use on large 
heating systems. The outlet of this air valve is 

three-quarters of an inch 
Air Valves. in diameter. It is particu- 

larly designed to take care 
of the air in the building and tunnel mains. The 
ordinary sized valve used in radiators is entirely in- 
sufficient to take care of large mains. Piping that 
is 4 inches and over should have the larger valves. 



Notes on Heating and Ventilation 245 

With still larger piping, lo or 12 inches in diameter, 
where the mains are 400 or 500 feet long, even this 
size is hardly sufficient to take care of the air 
unless a number of them are used. 

The valve shown in Fig. '/2 is often used. This 
consists of a brass pipe ''A" four feet long, to 
which is screwed a i54-in^ch angle valve. This 
pipe and angle valve are attached by a suitable el- 
bow and nipple to the main from the point at which 
the air is to be removed. A yoke is fastened at elbow 
''B'' and to this yoke tw^o iron rods are attached. 
These iron rods are connected at the other end of 
the yoke ''C' Yoke ''C" is attached to the valve 
stem of the angle valve. The threads are removed 
from the stem of the valve so that the valve will 
pass freely through the stuffing box. By means of 
a lock nut on the valve stem the height of the valve 
disc above the seat may be adjusted. To start with, 
however, the brass rod ''A'' will be cold and the 
valve disc will be off the valve seat and air will be 
allowed to pass out pipe ''D." The size used is 
usually iy\-\xiz\i pipe. As soon as steam comes the 
brass pipe *'A'' expands, bringing the valve seat up 
against the disc and closing the valve so that no 
steam can escape. 

Another arrangement that may be used is shown 
in Fig. 73. At the point at which it is desired to re- 
move the air a i-inch pipe is tapped into the fitting. 
Into this is tapped a i-inch nipple, an elbow and a 



246 Notes on Heating and Ventilation 




Figure 7 



This form of air valve is often used. 



short piece of pipe, as shown. At the end of this 
short piece of pipe is attached a gate valve. At 
intervals alon^;- the inside of the pipe are attached 



Notes on Heating" and Ventilation 247 

large air valves, such as the one shown in Fig. 71. 
On starting up the system the gate valve is left 
wide open and remains open until steam begins to 
blow, then this gate valve is closed and the small 
air valves take care of the accumulation of air that 
occurs from time to time. 




Figure 73. Air valve to relieve a titring and line of pipe 

from air. 

Lack of proper air valves may cause serious acci- 
dents in the pipe system. In large pipes 
when steam is turned on it will circulate along 
the top of the pipe and the cold air remains 
at the bottom of the pipes ; the upper side of 
the pipe will then be hotter than the lower 
and hence will expand more than the under 
side. The tendency of the pipe is to assume a cir- 
cular form, as shown in Fig. 74 l3y dotted lines. In 
case of a very large pipe this has been known to 



248 Notes on Heating and Ventilation 

wreck the piping system, breaking flanges and 
springing the valve seats. Such a condition may 
be prevented by running the air pipes on the mains 
down to the bottom of the main, as shown in the 
fig-ure, so that the air is removed from the bottom 
of the main instead of from the top of the main. In 
long piping systems it is very desirable that at in- 
tervals of not more than loo feet air valves should 
be placed to remove the air from the bottom of the 




Figure 74. How air collects and sometimes breaks a piping 
system. How it is prevented. 

main. The size of these valves w^ill depend upon 
the size of the main and they should be of ample 
capacity. It is not always necessary to use auto- 
matic valves. Automatic valves can be replaced 
by ^-inch or ^-inch valves for this purpose. 

Air valves should be located at all high points 
on the return mam, particularly at points where the 
return main rises, passes along the horizontal, and 
then drops down again. At such points air valves 
should be located at the top of the main. If this is 



Notes on Heating and Ventilation '-^49 

not clone the air wiH accumulate at these high points 
and prevent passage of water, sometimes almost as 
effectively as though the main were valved at these 
points. 

Surge tanks, traps and other devices where air 
may accumulate should be provided with air valves. 
In fact, when trouble is experienced in a steam pipe 
system one of the first things that the builder should 
assure himself of is that the air is being properly 
rem.oved from the parts of the system. 

COMBINATION OF STEAM AND HOT WATER 

SYSTEM. 

There are a number of systems using a combina- 
tion of exhaust steam and hot water for use in con- 
nection with central heating systems. The exhaust 
from the engine is passed through an exhaust 
heater and the water heated in this heater is circu- 
lated through the heating system by means of a 
pump. In this way exhaust steam can be used for 
heating a large territory without producing any 
back pressure. This form of heating may be used 
in connection with a condensing engine. The water 
being circulated by a pump under pressure insures 
its actual circulation throughout the whole system 
and makes possible the use of relatively small mains 
for heating purposes, smaller than would be re- 
quired for either low pressure steam or exhaust 
steam. In addition to the exhaust steam heater 



250 Notes on Heating and Ventilation 

there may be used either a hot water boiler or an 
auxihary Hve steam heater, so that in case the ex- 
haust is insufficient for heating the water, the w^ater 
may be passed through this hve steam heater, bring- 
ing it up to the proper temperature. In some cases 
a Greene economizer has been used for furnishing 
additional heat, thereby making use of the waste 
from the boiler. 

Systems of this kind have been installed in a 
number of cities and as high as one thousand houses 
heated from a central heating system. In these 
hot water circulating systems two general forms of 
pump are used, either a centrifugal pump driven 
by a motor or engine, or a piston pump of the ordi- 
nary type. In most cases unless a high pressure is 
desired, a centrifugal pump is desirable. The cen- 
tral hot water heating system has one particularly 
desirable feature — the hot water leaving the sys- 
tem may be adjusted to correspond with the exter- 
nal temperature. The size of hot water mains is de- 
termined from the velocity of water circulating in 
the main. In small mains it should not exceed 4 
feet per second ; in large mains it may be as high as 
8 feet per second. 

Central heating by means of hot water is par- 
ticularly adapted for residence districts, as the sys- 
tem can be installed with less expense per foot of 
main, making it possible to cover profitably an area 
having the houses scattered. Central heating with 



Notes on Heating and X'entilation 251 

steam is particularly adapted for close business dis- 
tricts where steam is the usual form of heating and 
where the piping system will be relatively short for 
the load carried. 

In connection with the systems using pressure 
there must be used some form of expansion tank. 
Some of these systems use an open expansion 
tank, allowing the water in the return system to 
enter this open tank at practically atmospheric pres- 
sure, the suction of the circulating pump being con- 
nected to this open tank. Where this system is used 
a piston type of pump would probably be a desirable 
form. AMiere the centrifugal type of pump is used 
it would be desirable to use a closed tank. In this 
case the tank is partly filled with water and partly 
filled with air. The expansion and compression of 
the air allows for the change in the volume of water 
due to changes of temperature conditions. In this 
case the pump will then only furnish the pressure 
necessary to overcome the resistance of the piping 
system. The air side of the expansion tank should 
be provided with an air pump, so that pressure may 
be maintained by means of an air pump on the air 
side of the system and the proper quantity of air 
carried in the tank at all times. 



CHAPTER XIII. 



PIPING, COVERING AND OTHER APPLIANCES. 

In all piping installation it is customary to cover 
the distributing pipes, except radiator connections. 

It is good practice to cover 
Pipe Covering. the risers passing through 

buildings, together with all 
steam and return mains. Where the water mains 
pass through rooms in which any drip from the 
pipes would be objectionable, such pipes are also 
covered to prevent the condensation of moisture on 
the outside of pipes. In general the best form of 
non-conductor is dry air, which is so confined as to 
prevent circulation. In all successful forms of cov- 
ering air is confined in the structure of the covering 
and the efifectiveness of the covering depends largely 
upon the confining of this air. The efifectiveness of 
different forms of covering was determined in a 
series of experiments made under the direction of 
Prof. ]^I. E. Cooley, University of ^lichigan. Table 
39 shows the relative efifectiveness of some of the 
dififerent forms of covering. 

The results of these tests show that hair felt is 
the best non-conductor. It is not, however, suited 
for over lo pounds pressure, as it chars and breaks 



Notes on Heating and Ventilation 253 

down at liigher pressure owing to the higher tem- 
perature ; this is also true of the wool felts. In 
low^ pressure work at such temperatures as are 
ordinarily used, hair felt is found to be quite sat- 



Table XXXIX. 
Relative Value of Different Pipe Coverings. 

S' .= c £ ^ ';2 CI > •= V- .E *- 

o w ii S a •- c ~ :;? i *: ^- •- £ a; 

■Si 3 ;/ ^ ^ -^ c J S^ - u. ^ 3 - 

1. Asbestos 145 .319 1.23 136. .803 

2. Magnesia 119 .224 .94 166. .915 

3. Magnesia and asbestos. .125 .500 1.12 118. .879 

4. Asbestos and wool felt .190 .228 1.12 102. .910 

5. Wool felt 117 .234 1.16 110. .904 

6. Wool felt and iron with 

air space 134 .269 . 125. .828 

Sectional Coverings. 

7. Mineral wool 097 .193 .94 91. .952 

8. Asbestos sponge 105 .220 1.12 102. .920 

9. Asbestos felt 100 .217 1.35 94. .923 

10. Hair felt 080 .186 1.45 75. .960 

Non-Sectional Coverings. 
Two layers asbestos 

paper 388 .777 364. .268 

Two layers asbestos 
paper, one inch hair 
felt and one thickness 

canvas 070 .150 68. 1,000 



isfactory. It is expensive, but its expense is war- 
ranted in the saving from condensation in the 
piping. 

Table 40 shows the relative effectiveness of dift'er- 
ent thicknesses of covering. Column 3 of this table 



254 Notes on Heating and Ventilation 

shows the relative effectiveness of the various thick- 
nesses of covering compared with the bare pipe. 
From this table it is not a difficult matter to figure 
the amount of saving that may be made by using 
various thicknesses of covering. Knowing the 
amount of steam carried per year and the cost to 
produce i,ooo pounds of steam, and having the 
results shown in this table, we can easily compute 
the financial savine to be made in the various thick- 



Table XL. 
Heat Transmission for Varying Thiclinesses of Covering. 

Ratio of B. T. IJ.'s 

Condensation of condensa- trans- 

Tliickness of per sq. ft. per tion covered mitted per 
covering, liour in pounds, to bare pipe. sq. ft. per hour. 

V^ .120 .281 167. 

% .117 .255 163. 

1 .107 .231 149. 
IV2 .099 .219 138. 
1% .087 .191 121. 

2 .078 .19 108. 

Tlie covering used in obtaining the above results was 
a wool felt. ^ 



nesses of covering. In doing this it is usually found 
that for building work an inch covering is suf- 
ficientl}' heavy ; but for tunnel work and all work- 
where the heat loss from the pipe is entirely lost 

• 

and does not enter the building it is economy to use 
covering 2 inches thick. Table 41 shows the heat 
lost through a i-inch wool covering with various 
steam pressures. In covering a pi]:)ing system the 



Notes on Heating and Ventilation 255 

fittings and valves should be covered the same thick- 
ness as the pipe. This also applies to flanges and 
steam traps. Where flanges and other parts which 
require removal are covered they should be covered 
so that the covering can be taken ofif easily. A sat- 
isfactory method of doing this is to form a cover- 
ing composed of one layer of asbestos paper, i inch 
of hair felt and one thickness of 8-ounce duck. 
These are quilted together with cord so that the 



Heat 


Table XLI. 

Transmission for Varying Pressures. 


Condensation 
Gauge per sq. 
pressure, ft. per hour. 


Ratio of 
condensation 
of covered 
to bare pipe. 


B. T. U.'s 

transmission 

per sq. 
ft. per hour. 


5.3 

9.6 

15.5 

20.5 


.108 
.111 
.126 
.134 . 


.239 
.233 
.227 
.223 


100. 
104. 
110. 
119. 



jacket is firmly held in one piece. This covering is 
then fastened over the pipe to be covered by means 
of hooks and laces. The advantas^e of coverino: 
may be shown from the following computation : 

Example. — In a given steam plant it was found 
that the heat lost from bare pipes per hour was 
3,355,000 B. T. U's. In the particular plant in 
question the number of heat units required to make 
a pound of steam was 990, and this loss of heat 
would represent a condensation of 3,390 pounds of 



256 Notes on Heating and Ventilation 

steam per hour. Assuming an evaporation of 9 
pounds of steam per pound of coal this would be 
equivalent to 376 pounds of coal per hour. If the 
plant were operated 365 days in the year and 20 
hours a day, and the coal cost $3.25 per ton, the 
yearly loss would be $2,069. ^Y covering the pipe 
I inch thick with hair felt the loss which would re- 
sult from the bare pipe would be reduced 15 per 
cent, which equals $314, making a saving of $1,755 
by putting on covering. This amount capitalized at 
10 per cent would represent an investment of $17,- 
550. In the particular case in question the actual 
cost of the covering was but $3,500. 

In steam piping work it is very important that the 
piping system be provided with sufficient number of 

properly located air valves. Pri- 
Air Valves. marily, air valves should be located 
at the points in the piping at 
which air accumulates in quantity. We are familiar 
with the fact that when a radiator is not provided 
with an air valve steam will not circulate into it 
and it does not become warm. This is true of both 
steam mains and the return system. The writer has 
seen the entire return system of a building plugged 
with air on account of there being no air valve on a 
high point in the return main. 

For radiators an air valve similar to that shown 
in Fig. 75 is usually used. You will notice tli^at this 
air valve allows air entering from the connection 



Notes on Heating and Ventilation 



257 



to the radiator to pass directly to the top of the air 
valve body and out through a small hole or open- 
ing, which may be adjusted by means of a screw 
plug. If water enters the air valve, the water will 
rise in the valve body until the copper float, having 
a pin on its upper end, rises so as to close the exit 





Figure 75. Type of air 
valves commonly used on 
radiators. 



Figure 76. Air valve 
used on radiators in con- 
nection with Paul valve. 



from the air valve, and no water is allowed t^ 
escape. When steam enters the air valve the ex- 
pansion plug shown at the center of the air valve 
expands, raising the copper float, again closing the 
outlet from the air valve. 

Fig 76 shows an air valve which is used for radi- 
ators in connection with a system of air piping 
from the air valves. (i) is a cap screw screwed 



268 Notes on Heating and Ventilation 

down on the valve with a lead washer, making 
a tight seat. (2) is a hollow screw upon which 
the expansion post (3) sets, closing the valve. 
The adjustment of the valve is done with 
screw (2), and this may be done without disturb- 
ing the valve. (3) is a hollow part fastened at (5) 
and held in place by the union (6). This should 
never be disturbed. (4) is the nipple of the valve 
body, by which it is attached to the radiator. This 
is the union for attaching to the piping of the Paul 
>ystem or other air piping system. (7) is a nut 
which forms the union for attaching this piping. 
The operation of the valve is as follows : The air is 
drawn in from the radiator through nipple (4) into 
the valve between the adjusting screw (2) and the 
composition part (3) passing down through (3) 
into the pipe. Wh^n steam enters the composition 
part becomes heated and expands, thereby closing 
the opening between (3) and (2). When air again 
accumulates and cools this composition part con- 
tracts, permitting air to be drawn through the tube. 

There are two typical forms of air valve, one 
closing off the air by the action of the float, the 
other closing off the air by the action of heat ex- 
panding a plug. V\^. 75 shows a combination of 
these two principles, which prevents the throwing 
of water or the discharging of steam. 

Fig. 76 exemplifies the simple expansion opera- 



Notes on Heating and Ventilation 259 

tion. The valve shown in Fig. 76 would allow cold 
water to pass. 

Fig. yy shows an air valve particularly adapted to 
hot water work. In this air valve the float prin- 
ciple alone is used. Air enters in through the con- 




Figuie 77. Air valve adapted to hot water work. 

nection to the radiator, as shown by the arrow in 
the cut, passes under the float and escapes through 
a small tube which reaches to a point near the top 
of the air valve. As soon as the water enters the 
float lifts, due to the air compressed by the water 
under the float, and the rubber valve held by the 
rim closes the opening through which the air 
escapes. The valve as shown here is made for 
connection to an air valve piping system. A similar 
valve is made without this connection. In the air 



260 Notes on Heating and Ventilation 

valve shown for connection to a piping system there 
is a three-way plug cock in the air valve, which al- 
lows of air and water being drawn directly to the 
air pipe system and of being entirely closed off. 

The pipe used in steam heating work is usually 
of standard weight, except for boiler blow-offs and 

boiler feed pipes, which are 
Pipe, Valves and Fittings, made of extra heavy pipe. 

Steam pipe is made of 
steel or wrought iron. Wrought iron is more ex- 
pensive than steel, but gives better results. Steel 
pipe can be made which is very satisfactory, but 
care should be used in selecting a good grade of 
pipe. Cast iron elbows and tees are more satisfac- 
tory than malleable iron and they should be full 
weight. There are on the market light-weight cast 
iron fittings. The advantage of cast iron for fittings 
is that the fittings can be broken with a sledge if at 
any time it is desired to open the pipe. If malleable 
iron fittings are used it is necessary to cut them out 
with a cold chisel, which is expensive. In putting 
up piping bushings are to be avoided as much as 
possible and reduction in size made in the fittings. 
Valves 2 inches and under are usually made of 
brass composition and should be of full weight. 
Over 2 inches it is customary to use iron body brass 
mounted. Valves over 4 inches should be provided 
with yokes. Valves 6 inches and over should be 
provided with by-passes. 



CHAPTER XIV, 



AUXILIARY DEVICES FOR HEATING SYSTEM. 

A temperature regulator is an automatic device 
which will open and close the valve of the radiator 
so as to keep the room at a constant tempera- 
ture. The temperature regulator in general 
consists of three parts. First, a thermostat which 
is so constructed that its parts will move with a 
change of temperature in the surrounding air and 
the motion of these parts will directly or indirectly 
open the dampers or valves wdiich control the heat 
supply. Second, there must be some means of 
transmitting the motion from the parts of the ther- 
mostat to the valves or dampers controlling the heat 
supply. Third, some form of mechanism for open- 
ing the valves or dampers. In most temperature 
regulating systems the thermostat merely fur- 
nishes power enough to close or open an air valve 
or electric sw^itch and thus start or stop the opera- 
tion of the valves or dampers. 

The form most used at the present time uses com- 
pressed air to operate the valves and dampers. In 
the Johnson thermostat a small air valve is opened 
by the expansion of a curved strip composed of two 



262 Notes on Heating and Ventilation 

materials having dififerent rates of expansion. The 
bending of this strip due to change of temperature 
allows the air to escape and a small diaphragm to 
move back, thus opening a second valve allowing 
the air to come from the compressor or source of 
air supply and close the valve or damper on the 
radiator. When the room becomes cool the con- 
traction of this strip closes the first small valve forc- 
ing out the diaphragm and closing ofif the compressed 
air supply to the valve or damper and releasing 
the air already in the valve or damper. Another 
form of thermostat extensively used is operated by 
means of a liquid confined in a thin metal vessel, 
the liquid having a very high degree of expansion. 
As the liquid expands or contracts it controls the 
system of valves controlling the heat supply to the 
room. 

Temperature regulation is a desirable thing in all 
large heating systems, particularly for public build- 
ings. The systems are quite expensive, but the 
expense of construction is more than offset by the 
saving in fuel bills. The saving in fuel bills in most 
cases is not less than 20 per cent and often as high 
as 30 per cent. In general the operation of these 
systems has been entirely satisfactory even after 
they have been in use some time without any attend- 
ance. The control of the temperature of the room 
should be regulated within 3 degrees. With proper 
care these systems should control the temperature 



Notes on Heating and Ventilation 263 

of the room within 2 degrees. Temperature regu- 
lating apparatus is particularly desirable in school 
rooms ; this places the temperature of the room out- 
side the control of the instructor and it is then free 
from his own personal ideas in the matter, thus 
adding much to the health and comfort of the occu- 
pants of the room. 



The discharge of air 



Air Piping System. 



from the air valves and ra- 
diators often produces a 

very disagreeable odor and in addition it is very 
difficult to obtain an air valve which will not at 
times discharge a certain amount of steam or water. 
This difficulty may be overcome by using an air 
valve so designed that the discharge connection to 
the valve can be fastened to a piping system. The 
pipes and air valves are carried to the basement, 
collected into a larger pipe and discharged to a 
sew^er or suitable vessel. A system of air piping is 
very desirable, particularly in large buildings, such 
as hotels and office buildings, where it saves ma- 
terially in the attendance necessary to keep the plant 
in operation. It is also desirable in nice residences 
where any discharge of water or steam might in- 
jure the furnishings. In case it is desirable to 
install a vacuum system of heating this system, 
could be connected directly to a vacuum pump in- 
suring more rapid circulation in the radiation. 
It is alwavs desirable in a steam or hot water 



264 Notes on Heating and Ventilation 

heating plant, particularly steam, to install some 

form of dam])er regulator 
Damper Eegulators. on the boiler. In some 

heating plants it consists of 
an ordinary rubber diaphragm enclosed in a metal 
case. The steam is allowed to come in contact with 
one side of the diaphragm, pushes a lever attached 
to the other side of the diaphragm. This lever op- 
erates a damper controlling the air supply to the 
fire and sometimes also operates the check valve 
in the breeching. This is a very desirable arrange- 
ment as it reduces the attendance necessary to keep 
the pressure in the boiler at the point desired. 

The humidity of the atmosphere is a very im- 
portant consideration in any heating system. When 

the air is very dry it is 
Humidity Regulation, necessary for a room to 

have a much higher tem- 
perature in order that it may feel comfortable than 
when the air is moist. It is, therefore, important 
that we keep the humidity at a point as high as 
consistent with satisfactory operation. Cold air 
contains proportionately less moisture than warm 
air and therefore when cold air is heated and 
brought into a building, it should be moistened in 
order to keep a proper per cent of humidity. The 
average humidity is about 70 per cent ; in the most 
arid regions humidity is as low as 30 per cent. Hu- 
midity as low as 30 per cent produces irritation of 



Notes on Heating and Ventilation 265 

the lungs and smarting of the eyes. In cold 
weather, if the humidity of the outside air is 70 
per cent and this air is heated and brought into 
the room without moistening, its humidity may be 
reduced as low as 30 or 35 per cent, making the 
air as dry as in the most arid regions. This pro- 
duces a serious effect upon the inhabitants and 
also the furniture of the room. The decrease of 
humidity due to the action of the heating system 
occurs particularly in the indirect heating system. 
There has been placed on the market wdiat is called 
a humidostat. This is similar to a thermostat ex- 
cept that it is arranged so that as the moisture de- 
creases in the room the humidostat opens up a se- 
ries of steam or water jets in the air supply so that 
the air in passing through the steam or water jet 
takes up moisture. When the moisture gets to a 
certain percentage, determined by the setting of 
the humidostat, the apparatus closes ofif automatic- 
ally the steam or water jets. Such devices are 
particularly desirable in connection with school 
and hospital heating plants. 

In the large cities the smoke and dust in the air 
makes ■ it undesirable to introduce this air directly 
into the room for ventilat- 
ing purposes. A great Air Washers, 
many schemes have been 

tried to remove the dust from the air. The earliest 
form was to use burlap screens through which the 



Notes on Heating and Ventilation 267 

air passes. These screens work fairly well but the 
finer dust will always be carried through tliem. A 
better plan is to pass the air through a sheet or 
series of sheets of water. After passing through 
these sheets of water the air is passed through an 
apparatus which removes the excess of water. Fig. 
78 shows the general arrangement of an air wash- 
ing system. As you will notice from the figure, the 
air first passes through a tempering coil which 
raises the temperature from 60 to 70 degrees, then 
passes through the sprays or sheets of water, then 
through the eliminator where the excess of water 
is removed and then it passes to the heating coils 
to be heated. The water used for washing the air 
is circulated over and over again by means of a 
small centrifugal pump driven by a motor. In 
some cases it is desirable that the air should be 
cooled. This may be done by placing cooling coils 
in the tank where the water collects after having 
washed the air, and reducing the temperature of 
this water to the desired point. The washing of the 
air with water also increases the humidity of the 
air. In a plant installed by the author the humidity 
of the air has been kept at a point not lower than 
60 per cent by means of the air washer. Air wash- 
ing devices are very effective in removing dirt ; the 
amount of dirt removed in some cases is very large. 
There is very frequently installed in connection 



268 Notes on Heating and Ventilation 

with the heating system what is known as a vacuum 

heating system. There are 
Vacuum Systems. two principal forms of 

vacuum heating systems, 
one in which the air is drawn from the radiator by 
means of an air pump through an air valve, as 
shown in Fig. 76, and the other in which the radia- 
tor is fitted with a special form of return 
valve and vacuum is maintained on the re- 
turn, system by means of a pump or aspira- 
tor. The vacuum systems of heating lowers 
the temperature of the radiator and the radiators 
do not condense so much steam as they would un- 
der full pressure. They do not make any material 
saving in the amount of coal burned. The prin- 
cipal advantages of the vacuum systems are cer- 
tainty of circulation and the reduction of pressure 
in the piping system. They are particularly well 
adapted for use in connection with exhaust steam 
heating systems where the reduction of pressure in 
the heating system lowers the back pressure on the 
engine, increasing the horse power output of tlie 
engine. 

The vacuum system of heating in which the air 
is drawn from the air valves is particularly de- 
sirable in hospitals and school buildings as it does 
away with the objectionable odor from the air 
valves. I lie vacuum system of heating does away 
very largely with the attendance required by air 



Notes on Heating and Ventilation 269 

valves. It also permits of the radiator being placed 
lower than the level of the boiler and the condensa- 
tion is raised from the lower level by means of the 
vacuum in the svstem. Oftentimes this enables the 
engineer to overcome serious difficulties in the de- 
sign of a heating plant. These systems can be 
profitably installed in old plants where the steam 
mains are overtaxed, owing to frequent additions 
to the plant. By additions of the vacuum system 
these old mains can be made to carry a larger 
weight of steam, the vacuum system permitting 
a higher velocity of steam in the system without 
increasing the back pressure. 



Sizes of Flow and Return 
Steam Mains 




Being an apprentice's query as 
to correct sizes of pipes in heat- 
ing plants, and answers thereto 
by twenty-five leading American 
heating engineers. These re- 
plies, giving the practice in some 
of the leading shops in many 
different cities of the country, 
with tables and diagrams, are 
by the following engineers : 



Prof. R. C. Carpenter, Cornell University 
Prof. J. H. Kinealy, St. Louis 

John Gormly, Philadelphia 

Ralph CoUamore, Detroit 

Gerard W. Stanton, New York 
Wm. G. Snow, Boston 

Thomas Barwick, New York 

EA. K. Munroe, Baltimore 

W. R. Stockwell, Irvington-on-Hudson 

Clarence M. Lyman, Utica, N. Y. 
R. R. M. Carpenter, Wilmington, Del. 
E. F. Capron, Chicago 

J. R. Shanklin, Charleston, W. Va. 

John S. Brennan, Milwaukee 

H. A. Smith, New York 
R. S. Thompson, Springfield, O. 

Bernard Gause, Jacksonville, 111. 

J. J. Wilson, Philadelphia 

Henry S. Kries, Baltimore 

Reginald Pelham Bolton, New York 
F. R. Still, Detroit 

Thomas Morrin, San Francisco 

James A. Donnelly, New York, and others. 

Bound in Beards, r-j • r r\ . i i- j 

6Kx4>iinchei rrice DU cents, dehvered 
Domestic Engineering, 58-64 N. Jefferson St., Chicago 



Plumbing Catechism 

THEORY AND PRACTICE OF 
PLUMBING DESIGN 




By Charles B. Ball, M. Am. 
Soc. C. E., and M. Am. Soc. In- 
spectors of Plumbing and Sani- 
tary Engineers, and Herbert T, 
Sherriff, A, B., some-time Edi- 
tor of "Domestic Engineering", 
M. Am. Soc. Inspectors of 
Plumbing and Sanitary Engi- 
neers. 



Bound in cloth; 6}i x4^; 1 00 pp; elaborately indexed. 

This book formulates, in question and answer form, the basic 
principles of plumbing design and practice, crystallizing the knowledge 
of the skilled plumber, and providing the non-technical reader a source 
of information as free as possible from puzzling set phrases. It is 
sepecially commended to students in engineering and trade schools, 
and to master and journeymen plumbers, preparing for examinations. 
It does not discuss matters of handicraft such as joint wioing, lead 
burning, etc. 

CONTENTS: PLUMBING FIXTURES: Lavatories, kitchen sinks, 
bath tubs, laundry tubs, slop sinks, urineds, water dosets, water closet flushing 
apparatus, local ventilation, floor slabs, refrigerators. WATER SERVICE 
PIPELS: Fixture supply pipes, storage tanks, hot water supply systems. THE 
DESIGN OF PIPE SYSTEMS: The main drain, the main trap, the air inlet, 
traps, ventilation pipes. PUMPS. EFFECTS OF FREEZING. 

Price $1.00, delivered 
Domestic Engineering, 58 64 N.Jefferson St., Chicago 



FIFTY 

Plumbing Charts 




Showimg how modern, up- 
to-date, sanitary plumbing 
should be done. Paper 
bound, 9x5 yi inches; 50 pp. 
A lay-out of each of the fol- 
lowing jobs is shown, giving 
sizes of all pipes, heights of 
all fixtures; every joint, every 
piece of material and every 
fixture: 



Plate 



1 Kitchen Sink Connection 


Plate 


: 27 Anti-Freezing W. C 


2 Lavatory 






28 Roof Connections 


3 Water Closet 






29 Roof Connections 


4 Bath Tub 






30 Fresh Air Inlet 


5 Wash Tray \ 




<< 


3 1 Fresh Air Inlet 


6 Pantry Sink 




<4 


32 Traps 


7 Urinal 




it 


33 Traps 


8 Slop Sink 




• < 


34 Traps 


9 Hotel Sink 




4t 


35 Grease Traps 


lOSitzBath 




<( 


36 SoU Pipe on Side Wall 


1 I Foot Bath 




4« 


37 Plumbing fcJr Residence 


1 2 Bath Room 




«t 


38 Cellar Work, Residence 


13 Refrigerator 




it 


39 Plumbing for Double House 


1 4 Refrigerator Line 






Under Test 


1 5 Ferru e Connections 




40 Plumbing for 3 Tenement houses 


1 6 Preparing Lead Works 




4 1 Plumbing for Six Flats 


1 7 Ferrule Connections 




42 Cellar Work for Stores and Flats 


1 8 Cleanouts 




43 Plumbing for Horse Stall 


19 Water Closets 




44 Plumbing for Stables 


20 Water Closets 




45 Plumbing for Eng. House 


21 Back Venting 




46 Cellar Work, Eng. House 


22 Back Venting 




47 Plumbing for Hotel 


23 Floor Con. for W. C. 




48 Plumbing for R. R. Sta. 


24 Roor Con. for W. C. 




49 Plumbing for Y.M.C. A. Bldg. 


25 Local Venting 




50 Plumbing, High School 


26 Local Venting 









Price 25 cents, delivered 
Domestic Engineering, 58-64 N. Jefferson St., Chicago 



JUL 3 1908 



